Z80 Simulator v7.4 serial key or number

Manufacturer	Commodore Business Machines (CBM)
Type	Home computer
Release date	; 35&#;years ago&#;()
Discontinued	; 31&#;years ago&#;()
Units sold	&#;million worldwide
Operating system	Commodore BASIC Digital ResearchCP/M GEOS
CPU	MOS @ 1–2&#;MHz Zilog Z80A, or Zilog Z80B @ 4&#;MHz
Memory	&#;KB (standard), &#;KB (with KB REU expansion RAM)
Graphics	VIC-II E (×, 16 colors, sprites, raster interrupt), MOS (RGBI × 16 colors, blitter)
Sound	SID / (3× Osc, 4× Wave, Filter, ADSR, Ring)
Predecessor	Commodore 64

The Commodore , also known as the C, C, C= ,^{[n 1]} is the last 8-bithome computer that was commercially released by Commodore Business Machines (CBM). Introduced in January at the CES in Las Vegas, it appeared three years after its predecessor, the bestselling Commodore

The C is a significantly expanded successor to the C64, with nearly full compatibility. The newer machine has &#;KB of RAM in two 64&#;KB banks, and an column color video output. It has a redesigned case and keyboard. Also included is a Zilog Z80 CPU which allows the C to run CP/M, as an alternative to the usual Commodore BASIC environment. The presence of the Z80 and the huge CP/M software library it brings, coupled with the C64's software library, gives the C one of the broadest ranges of available software among its competitors.^[1]

The primary hardware designer of the C was Bil Herd, who had worked on the Plus/4. Other hardware engineers were Dave Haynie and Frank Palaia, while the IC design work was done by Dave DiOrio. The main Commodore system software was developed by Fred Bowen and Terry Ryan, while the CP/M subsystem was developed by Von Ertwine.^[2]

Technical overview[edit]

The BASIC prompt for the Commodore in column mode, running Commodore BASIC V

The C's keyboard includes four cursor keys, an Alt key, Help key, Esc key, Tab key and a numeric keypad. None of these were present on the C64 which had only two cursor keys, requiring the use of the Shift key to move the cursor up or left. This alternate arrangement was retained on the , for use under C64 mode.^[3] The lack of a numeric keypad, Alt key, and Esc key on the C64 was an issue with some CP/M productivity software when used with the C64's Z80 cartridge. A keypad was requested by many C64 owners who spent long hours entering machine languagetype-in programs.^[4] Many of the added keys matched counterparts present on the IBM PC's keyboard and made the new computer more attractive to business software developers.^[5] While the 's column mode closely duplicates that of the C64, an extra 1K of color RAM is made available to the programmer, as it is multiplexed through memory address 1. The C's power supply is improved over the C64's unreliable design, being much larger and equipped with cooling vents and a replaceable fuse. The C does not perform a system RAM test on power-up like previous Commodore machines. Instead of the single microprocessor of the C64, the C incorporates a two-CPU design. The primary CPU, the , is a slightly improved version of the , capable of being clocked at 2&#;MHz. The second CPU is a Zilog Z80 which is used to run CP/M software, as well as to initiate operating-mode selection at boot time. The two processors cannot run concurrently, thus the C is not a multiprocessing system.

The C's complex^[6][7] architecture includes four differently accessed kinds of RAM (&#;KB main RAM, 16–64&#;KB VDC video RAM, 2&#;kNibbles VIC-II Color RAM, 2-kilobyte floppy-drive RAM on CDs, 0, or &#;KB REU RAM), two or three CPUs (main: , Z80 for CP/M; the D also incorporates a in the disk drive), and two different video chips (VIC-IIe and VDC) for its various operational modes.^[8][9]

Early versions of the C occasionally experience temperature-related reliability issues due to the use of an electromagnetic shield over the main circuit board. The shield was equipped with fingers that contacted the tops of the major chips, ostensibly causing the shield to act as a large heat sink. A combination of poor contact between the shield and the chips, the inherently limited heat conductivity of plastic chip packages, as well as the relatively poor thermal conductivity of the shield itself, resulted in overheating and failure in some cases. The SID sound chip is particularly vulnerable in this respect. The most common remedy is to remove the shield, which Commodore had added late in development to comply with FCC radio-frequency regulations.

The C has three operating modes. C Mode (native mode) runs at 1 or 2&#;MHz with the CPU and has both and column text modes available. CP/M Mode uses both the Z80 and the ^[10] and is able to function in both or column text mode. C64 Mode is nearly percent compatible with the earlier computer. Selection of these modes is implemented via the Z80 chip. The Z80 controls the bus on initial boot-up and checks to see if there is a CP/M disk in the drive, if there are any C64/C cartridges present, or if the Commodore key (which serves as the Cmode selector) is being depressed on boot-up. Based on these conditions, it will switch to the appropriate mode of operation.

C mode[edit]

In , a year before the release of the Commodore , Commodore released the Plus/4. Although targeted at a low-end business market that could not afford the relatively high cost and training requirements of early IBM PC compatibles, it was perceived by the Commodore press as a follow-up to the 64 and would be expected to improve upon that model's capabilities. While the C64's graphics and sound capabilities were generally considered excellent, the response to the Plus/4 was one of disappointment. Upon the Plus/4's introduction, repeated recommendations were made in the Commodore press for a new computer called the "C" with increased RAM capacity, an column display as was standard in business computers, a new BASIC programming language that made it easy for programmers to use the computer's graphics and sound without resorting to PEEK and POKEs, a new disk drive that improved upon the 's abysmal transfer rate, as well as total C64 compatibility.^[11][12]

The designers of the C succeeded in addressing most of these concerns. A new chip, the VDC, provides the C with an column color CGA-compatible display (also called RGBI for red-green-blue plus intensity). The then-new microprocessor is completely backward-compatible with the C64's , but can run at double the speed if desired. The C64's BASIC was replaced with BASIC , which includes structured programming commands from the Plus/4's BASIC , as well as keywords designed specifically to take advantage of the machine's capabilities. A sprite editor and machine language monitor were added. The screen-editor part of the Kernal was further improved to support an insert mode and other features accessed through ESC-key combinations, as well as a rudimentary windowing feature, and was relocated to a separate ROM. The VIC-II chip which controls the column display can only operate at 1&#;MHz, so the column display appears jumbled in mode. In column mode the editor takes advantage of VDC features to provide blinking and underlined text, activated through escape codes, in addition to the standard Commodore reverse text.^[13] The C's column mode can display lowercase characters along with PETSCII graphics characters; column mode is subject to the same "upper- and lowercase" or "uppercase-plus-graphics" restriction as earlier Commodores.^[14] The and column modes are independent and both can be active at the same time. A programmer with both a composite and RGB display can use one of the screens as a "scratchpad" or for rudimentary multiple buffer support. The active display can be switched with ESC-X.^[15] A hardware reset button was added to the system. The keyboard, however, was not switched to the Selectric layout as had become standard, instead retaining the same ADM-3A-derived design as on Commodore's prior models.

The back of the Commodore

The VDC chip is largely useless for gaming since it has no sprites or raster interrupts. NTSC Cs will work with any CGA-type monitor (TTL RGB @ 15&#;kHz/60&#;Hz) such as the IBM However, PAL models of the C operate at 50&#;Hz and aren't compatible with most CGA monitors, which expect a 60&#;Hz refresh rate. Pin 7 of the VDC output (normally unused on CGA monitors) produces a monochrome NTSC/PAL signal, but no cable was provided for it and interested users had to make their own or purchase one on the aftermarket.

Two new disk drives were introduced in conjunction with the C the short-lived single-sided and the double-sided A dual-disk model was announced but never produced. Later on, the inch was introduced. All of these drives are more reliable than the and promise much better performance via a new "burst mode" feature. The drive also has more on-board RAM than its predecessors, making it possible to open a larger number of files at one time. BASIC includes and commands to support loading and saving to disk without using the or other device number, and also a command that reads a disk's catalog information directly to screen memory without overwriting BASIC memory as in BASIC In addition, the C introduces auto-booting of disk software, a feature standard on most personal computers, but absent from Commodore machines up to that point. Users no longer have to type . BASIC also added a COLLECT command for removing "splat" files (files that were not closed properly and truncated to zero length).

All drives will normally start up in native mode on the C If the user switches to C64 mode by typing "GO 64", the drive remains in native mode. But if C64 mode is activated by holding the Commodore key down when powering-up, the then goes into mode. This routine is necessary for software that performs low-level drive access.

The C has twice the RAM of the C64, a far higher proportion of which is available for BASIC programming, due to the new MMU bank-switching chip. This allows BASIC program code to be stored separately from variables, greatly enhancing the machine's ability to handle complex programs, speeding garbage collection and easing debugging for the programmer. An executing program can be ped, its code edited, variable values inspected or altered in direct mode, and program execution resumed with the variable table intact using BASIC's command.^[16] Although other BASICs support the command to restart execution without clearing variables, editing any code causes them to be cleared.^[17] Different memory configurations can be loaded using BASIC's command.

BASIC has a full complement of graphics and sound-handling commands, as well as BASIC 's disk commands and improved garbage cleanup, and support for structured programming via IFTHENELSE, DOWHILE, and WHILEWEND loops. Programmable characters are still however not supported, so the programmer will have to manipulate them with PEEK and POKE as on the VIC and C

On the downside, BASIC ran considerably slower than BASIC unless 2&#;MHz mode was used due to its 28&#;KB size (a % increase over BASIC ) and having to bank switch to access program variables and BASIC program text (if greater than 16k in length).

The 's ROM contains an easter egg: Entering the command in native mode reveals a screen with a listing of the machine's main developers followed by the message Also, entering the keywords or will produce an . These commands are holdovers from the BASIC interpreter intended for a planned but never-produced LCD portable computer and had been intended to exit from the BASIC interpreter and to ignore keyboard input during sensitive program execution, respectively.

The C's greater hardware capabilities, especially the increased RAM, screen display resolution, and serial bus speed, made it a more capable platform than the C64 for running the GEOS graphical operating system.

CP/M mode[edit]

Using CP/M mode requires use of a boot diskette. The diskette was included with the computer, which did not include a disk drive.

The second of the C's two CPUs is the Zilog Z80, which allows the C to run CP/M. The C was shipped with CP/M (a.k.a. CP/M Plus, which is backward-compatible with CP/M ) and ADM31/3A terminal emulation. A CP/M cartridge had been available for the C64, but it was expensive and of limited use since the drive cannot read the MFM-formatted disks that CP/M software was distributed on. Software had to be made available on Commodore-specific disks formatted using the GCR encoding scheme. Commodore made versions of PerfectCalc and the EMACS-derived PerfectWriter available,^[18] and Commodore user groups sometimes had a selection of CP/M diskettes, but the limited software availability negated one of CP/M's chief attractions—its huge software library. In addition, the cartridges only work on early model C64s from and are incompatible with later units. Since they were also incompatible with the C, the design team decided to support CP/M by putting the Z80 on the main system board.

The C runs CP/M noticeably slower than most dedicated CP/M systems, as the Z80 processor runs at an effective speed of only 2&#;MHz. This was because the C's system bus was designed around the 65xx CPUs. These CPUs handle data and memory addressing very differently from the Z CP/M also ran more slowly due to the reasons mentioned below, such as needing to pass control to the for any I/O or interrupt processing. For these reasons, few users actually ran CP/M software on the C

When the C is powered on, the Z80 is active first and executes a small boot loader ROM at $0-$FFF to check for the presence of a CP/M disk. If one is not detected, control is passed to the and C native mode is started.

CP/M mode in practice requires a or drive to be useful, since a cannot read MFM disks and will run much slower due to not supporting the C's burst mode. CP/M boot disks nonetheless must be in the drive's native GCR format; MFM disks cannot be booted from, only read once the user is already in CP/M. This is because the code necessary to operate the drive in MFM mode is loaded as part of the boot process. In addition, column mode is generally required since most CP/M software expects an column screen. The C emulates an ADM-3A terminal^{[citation needed]} in CP/M mode, so software will have to be set up for that. Aside from the standard ADM-3A terminal commands, a number of extra ones are available to use the VIC-II and VDC's features, including setting the text and background color. The CP/M command interpreter (although not application software) includes a safeguard to prevent the user from issuing a control code to make the text and background the same color, which would render text invisible and force the user to reset the computer. If this happens, it will default to a gray background with brown text.

In CP/M mode, it is possible to run MBASIC, Microsoft's release of BASIC for CP/M. Compared with the native mode BASIC , MBASIC is terse and limited in its capabilities, requiring the use of terminal-style key combinations to edit program lines or move the text cursor and lacking any sound or graphics features. Although MBASIC has mathematical and calculation features that BASIC lacks such as integer and double precision variable support, any speed advantage gained by the use of integer variables is rendered moot by the extremely slow performance of the computer in CP/M mode. Moreover, Commodore BASIC has bit floating point which serves as a middle ground between MBASIC's bit floating point and bit double precision variables. MBASIC also offers only 34k of free program space against BASIC 's approximately 90k.

Other CP/M software such as Wordstar and Supercalc will also be significantly outperformed by native mode C equivalents like PaperClip, which also have an easier to use interface.

The CP/M CBIOS (the part of CP/M that interfaces with the hardware) does not directly interface with the hardware like on most CP/M implementations, rather it calls the kernal routines for interrupt handing and I/O—when the kernal needs to be used, the Z80 uses routines at $FFD0-$FFEF to pass parameter data to the , which is then activated and the Z80 deactivated. After the kernal routine is finished executing, control is passed back to the Z It was reported that the programmer in charge of porting CP/M to the C had intended to have the CBIOS interface with the hardware directly in Z80 machine language, but had great difficulty with the VDU chips as they were prone to overheating and self-destructing. The VDU also underwent numerous hardware revisions while the C was in development and the CP/M programmer was unable to get his code working properly, so the C engineering team requested instead that he simply rewrite the CBIOS to pass function calls to the ^[19][20]

CP/M mode is very different from the operating environments familiar to Commodore users. While Commodore DOS is built into the ROM of Commodore disk drives and is usually accessed through BASIC, CP/M requires the use of a boot diskette and requires entry of terse commands inherited from minicomputer platforms. CP/M programs tend to lack the user-friendly nature of most Commodore applications. Intended to give the new computer a large library of professional-grade business software that Commodore lacked, CP/M was long past its prime by the mids, and so it was seldom used on the C

C64 mode[edit]

Photo from the s showing a C set-up with two disk drives and two monitors displaying the independent and column screens. Many users continued to use the inherited from their C64 system as a second drive.

By incorporating the original C64 BASIC and Kernal ROMs in their entirety (16&#;KB total), the C achieves almost percent compatibility with the Commodore The C64 mode can be accessed in one of three ways:

• holding down the Commodore-logo key when booting the system
• entering the command, then responding to the prompt, in BASIC ^[21]
• booting with a C64 cartridge plugged in

Grounding the cartridge port's /EXROM and/or /GAME lines will cause the computer to automatically start up in C64 mode. This feature faithfully duplicates the C64's behavior when a cartridge (such as Simons' BASIC) is plugged into the port and asserts either of these lines but, unlike an actual C64, where the memory-map-changing action of these lines is implemented directly in hardware, the C's Z80 firmware startup code polls these lines on power-up and then switches modes as necessary. C native-mode cartridges are recognized and started by the kernal polling defined locations in the memory map.

C64 mode almost exactly duplicates the features of a hardware C The MMU, Z80, and IEC burst mode are disabled in C64 mode, however all other C hardware features including the VDU and 2&#;MHz mode are still accessible. The extended keys of the C keyboard may be read from machine language, although the kernal routines only recognize the keys that exist on the C A few games are capable of detecting if a C is running and switching to 2&#;MHz mode during the vertical retrace for faster performance.

On North American Cs, when in C64 mode, even the character (font) ROM changes from that of C mode. Early C prototypes had a single ROM, with a slightly improved character set over that of the C But some C64 programs read the character ROM as data, and will fail in various ways on a C Thus, the C was given a double-sized character ROM, which delivers the C font in C mode, and the C64 font in C64 mode. International models of the C use the unmodified C64 font in both modes, since the second half of the character ROM is instead dedicated to the international font (containing such things as accented characters or German umlauts).

Some of the few C64 programs that fail on a C will run correctly when the key is pressed down (or the ASCII/National key on international C models). This has to do with the larger built-in I/O port of the C's CPU. Whereas the key found on both C64 and C is simply a mechanical latch for the left key, the key on the C can be read via the 's built-in I/O port. A few C64 programs are confused by this extra I/O bit; keeping the key in the down position will force the I/O line low, matching the C64's configuration and resolving the issue.

A handful of C64 programs write to , often as part of a loop initializing the VIC-II chip registers. This memory-mapped register, unused in the C64, determines the system clock rate. Since this register is fully functional in C64 mode, an inadvertent write can scramble the column display by switching the CPU over to 2–MHz, at which clock rate the VIC-II video processor cannot produce a coherent display. Fortunately, few programs suffer from this flaw. In July , COMPUTE!'s Gazette published a type-in program that exploited this difference by using a raster interrupt to enable fast mode when the bottom of the visible screen was reached, and then disable it when screen rendering began again at the top. By using the higher clock rate during the vertical blank period, standard video display is maintained while increasing overall execution speed by about 20 percent.^[22][23]

An easy way to differentiate between a hardware C64 and a C operating in C64 mode, typically used from within a running program, is to write a value different from to memory address, a register which is used to decode the extra keys of the C (the numerical keypad and some other keys). On the C64 this memory location will always contain the value no matter what is written to it, but on a C in C64 mode the value of the location—a memory-mapped register—can be changed. Thus, checking the location's value after writing to it will reveal the actual hardware platform.

RAM setup[edit]

To handle the relatively large amounts of ROM and RAM (tenfold the size of 's 64&#;KB address space) the C uses the MMU chip to create different memory maps, in which different combinations of RAM and ROM would appear according to bit patterns written into the MMU's configuration register at memory address. Another feature of the memory management unit is to allow relocation of zero page and the stack.

Although the C can theoretically support k of RAM in four blocks, the PCB has no provisions to add this extra RAM, nor can the MMU actually access more than k. Therefore, if the MMU is programmed to access blocks 2 or 3, all that results is a mirror of the RAM in blocks 0 and 1.

Since the I/O registers and system ROMs can be disabled or enabled freely, as well as being locatable in either RAM bank and the VIC-II set to use either bank for its memory space, up to memory configurations are possible, although the vast majority of them are useless (for example, unworkable combinations like the kernal ROM in bank 0 and the I/O registers in bank 1 are possible). Because of this, BASIC's BANK statement allows the user to select 15 of the most useful arrangements, with the power-on default being Bank This default places the system ROMs, I/O registers, and BASIC program text in block 0, with block 1 being used by BASIC program variables. BASIC program text and variables can extend all the way to $FFEF. But since block 0 contains the ROMs and I/O registers from $ onward, BASIC uses an internal switching routine to read program text higher than $3FFF.

The top and bottom 1k of RAM ($0–$3FF and $FF$FFFF) are "shared" RAM, visible from both blocks. The MMU allows either to be expanded in increments up to 16k. The $0–$3FF range contains the zero page and stack while $FF$FFFF contains the MMU registers and reset vectors. These areas are always shared and cannot be switched to non-shared RAM. Shared RAM is always the opposite bank from the one currently being used by the CPU, thus if bank 0 is selected, any read or write to shared RAM will refer to the corresponding locations in bank 1 and vice versa. The VIC-II can be set to use either RAM bank and from there, its normal 16k window. While on the C64, the VIC-II can only see the character ROM in banks 2 and 4 of its memory space, the C, on the other hand, makes it possible to enable or disable the character ROM for any VIC-II bank via the register at $1. Also, there are two sets of color RAM—one visible to the CPU, the other to the VIC-II and the user may select what chip sees what.

In CP/M mode, the Program Segment Prefix and Transient Program Area reside in Bank 1 and the I/O registers and CP/M system code in Bank 0.

The C's RAM is expandable from the standard &#;KB to , or even 1,&#;KB, either by using commercial memory expansion modules, or by making one based on schematics available on the internet.^[24]

Commodore's RAM Expansion Units use an external DMA controller^[25] to transfer data between the C's RAM and the RAM in the expansion unit.

Commodore D[edit]

Late in , Commodore released to the European market a new version of the C with a redesigned chassis resembling the Amiga Called the Commodore D, this new European model featured a plastic chassis with a carrying handle on the side, incorporated a disk drive into the main chassis, replaced the built-in keyboard with a detachable one, and added a cooling fan. The keyboard also featured two folding legs for changing the typing angle.

According to Bil Herd, head of the Hardware Team (a.k.a. the "C Animals"), the CD was ready for production at the same time as the regular version. Working to release two models at the same time had increased the risk for on-time delivery and was apparent in that the main PCB has large holes in critical sections to support the CD case and the normal case concurrently.

In the latter part of , Commodore released a version of the CD in North America and parts of Europe referred to as the CDCR, CR meaning "cost-reduced". The DCR model features a stamped-steel chassis in place of the plastic version of the CD (with no carrying handle), a modular switched-mode power supply similar to that of the CD, retaining that model's detachable keyboard and internal floppy drive. A number of components on the mainboard were consolidated to reduce production costs and, as an additional cost-reduction measure, the 40 millimeter cooling fan that was fitted to the D model's power supply was removed. However, the mounting provisions on the power supply subchassis were retained, as well as the two volt DC connection points on the power supply's printed circuit board for powering the fan. The CDCR mounting provision is for a 60mm fan.

A significant improvement introduced with the DCR model was the replacement of the video display controller (VDC) with the more technically advanced VDC and equipping it with 64 kilobytes of video RAM—the maximum amount addressable by the device. The four-fold increase in video RAM over that installed in the "flat" C made it possible, among other things, to maintain multiple text screens in support of a true windowing system, or generate higher-resolution graphics with a more flexible color palette. Little commercial software took advantage of these possibilities.

The CDCR is equipped with new ROMs dubbed the " ROMs," so-named from the copyright date displayed on the power-on banner screen. The new ROMs address a number of bugs that are present in the original ROMs, including an infamous off-by-one error in the keyboard decoding table, in which the 'Q' character would remain lower case when CAPS LOCK was active. Some software will only run on the DCR, due to dependencies on the computer's enhanced hardware features and revised ROMs.^[26]

Despite the DCR's improved RGB video capabilities, Commodore did not enhance BASIC with the ability to manipulate RGB graphics. Driving the VDC in graphics mode continues to require the use of calls to screen-editor ROM primitives or their assembly language equivalents,^[27] or by using third-party BASIC language extensions, such as Free Spirit Software's "BASIC 8", which adds high-resolution VDC graphics commands to BASIC

Market performance[edit]

By January Info reported that "All of those rumors about the imminent death of the C may have some basis in fact." Stating that Commodore wanted to divert resources to increasing 64C production and its PC clones, the magazine stated that, "The latest word online is that the last C will roll off the lines in December of "^[28]Compute! stated in , "If you bought your under the impression that specific software would be plentiful and quick to arrive, you've probably been quite disappointed. One of the 's major selling points is its total compatibility with the 64, a point that's worked more against the than for it."^[26] Because the would run virtually all 64 software, and because the next-generation 32/bit home computers—primarily the Commodore Amiga and Atari ST—represented the latest technology, relatively little software for the C's native mode appeared (probably on the order of – commercial titles, plus the usual share of public domain and magazine type-in programs), leading some users to regret their purchase.^[29] While the C sold a total number of 4&#;million units between and , its popularity paled in comparison to that of its predecessor. One explanation for these lower sales numbers may be because the C64 was sold to people primarily interested in video games, which the more expensive C didn't add much value towards improving.

Some C64 software such as Bard's Tale III and Kid Niki ran in mode without stating this in the documentation, using the autoboot and the 's faster disk access.^[30] Some Infocom text adventures took advantage of the column screen and increased memory capacity. Some C64 games were ported to native mode like Kikstart 2 and The Last V8 from Mastertronic, which had separate C versions, and Ultima V: Warriors of Destiny from Origin Systems, which used extra RAM for music if running on the C Star Fleet I: The War Begins from Interstel had separate versions, and took advantage of column display on the C The vast majority of games simply ran in C64 mode.

By contrast, many C64 productivity software titles were ported to the C, including the popular PaperClip and Paperback Writer series.^[31] This software used the extra memory, column screen, enhanced keyboard and large-capacity disk drives to provide features that were considered essential for business use.^[32] With its advanced BASIC programming language, CP/M compatibility and "user-friendly" native software packages such as Jane, Commodore attempted to create a low-end business market for the C similar to its strategy with the Plus/4, even distancing itself from the home computer label by branding the C a "Personal Computer" on the case.^[33][34] Significantly, the C was the first Commodore computer to advertise its use of Microsoft BASIC, where the Microsoft name would have been a competitive asset.

The C was certainly a better business machine than the C64, but not really a better gaming machine. People who wanted business machines bought IBM PC clones almost exclusively by the time the C was released. The availability of low-cost IBM compatibles like the Leading Edge Model D and Tandy that, in some cases, sold for less than a complete C system derailed Commodore's small business computer strategy. There was a professional-level CAD program, Home Designer by BRiWALL,^[35] but again, most of this work was done on PCs by the C's era. The main reason that the C still sold fairly well was probably that it was a much better machine for hobbyist programming than the C64, as well as being a natural follow-on model to owners with significant investments in C64 peripherals.

But ultimately the C could not compete with the new 16/bit systems, which outmatched it and the rest of its 8-bit generation in nearly every aspect. When the C(D/DCR) was discontinued in , it was reported to cost nearly as much to manufacture as the Amiga , even though the CD had to sell for several hundred dollars less to keep the Amiga's high-end marketing image intact.

Bil Herd has stated that the design goals of the C did not initially include % compatibility with the C Some form of compatibility was always intended after Herd was approached at the Plus/4's introduction by a woman who was disappointed that the educational software package she had written for the C64 would not run on Commodore's new computer, but when Commodore's marketing department learned of this, they independently announced total compatibility. Herd gave the reason for the 's inclusion of a Z80 processor as ensuring this "% compatibility" claim, since supporting the C64's Z80 cartridge would have meant the C supplying additional power to the cartridge port. He also stated that the VDC video chip and Z80 were sources of trouble during the machine's design. Herd added that "I only expected the C to be sold for about a year, we figured a couple of million would be nice and of course it wouldn’t undercut Amiga or even the C64".^[36] After Commodore raised the price of the 64 for the first time by introducing the redesigned 64C in , its profit from each 64C sold was reportedly much greater than that from the C^[37]

Specifications[edit]

• CPUs:^[38]
  • MOS Technology @ 2 MHz (1&#;MHz selectable for C64 compatibility mode or C's column mode)
  • Zilog Z80&#;&#;@ 4&#;MHz (running at an effective 2&#;MHz because of wait states to allow the VIC-II video chip access to the system bus)
  • (CD(CR)): MOS Technology for the integrated floppy controller
• MMU: MOS Technology Memory Management Unit controls /Z80 processor selection; ROM/RAM banking; common RAM areas; relocation of zero page and stack
• RAM: KB system RAM, 2&#;KB 4-bit dedicated color RAM (for the VIC-II E), 16&#;KB or 64&#;KB dedicated video RAM (for the VDC), up to &#;KB REU expansion RAM
• ROM: 72 KB
  • 28 KB BASIC
  • 4 KB MLM
  • 8 KB C KERNAL
  • 4 KB screen editor
  • 4 KB Z80 BIOS
  • 16 KB C64 ROM: ≈9&#;KB C64 BASIC + ≈7&#;KB C64 KERNAL
  • 4 KB C64 (or international) character generator
  • 4 KB C (or national) character generator
  • 32 KB Internal Function ROM (optional: for placement in motherboard socket)
  • 32 KB External Function ROM (optional: for placement in REU socket)
• Video:
  • MOS / VIC-II E (NTSC/PAL) for column composite video (a TV set can be used instead of a monitor if desired)
    • Direct register access through memory-mapped I/O
    • Text mode: 40×25, 16 colors
    • Graphics modes: ×, ×
    • 8 hardware sprites
    • 2 KB dedicated 4-bit color RAM, otherwise uses main memory as video RAM
  • MOS VDC (or, in CDCR, the ) for column digital RGBI component video, compatible with IBM PCCGA monitors, monochrome display also possible on composite video monitors; usable with TV sets only when the set has SCART and/or baseband video-in sockets in addition to the antenna connector. Color is possible through SCART, only monochrome through baseband video-in.
    • Indirect register access (address register, data register in mapped memory)
    • Text mode: Fully programmable, typically 80×25 or 80x50, 16&#;RGBI colors (not the same palette as the VIC-II)
    • Graphics modes: Fully programmable, typical modes are x, ×, and × (interlaced).
    • 16 KB dedicated video RAM (64&#;KB standard in CDCR, C/CD can be upgraded to 64&#;KB), accessible to the CPU only in a doubly indirect method (address register, data register on VDC, which in turn are addressed through address register, data register in mapped memory)
    • Limited blitter functionality
• Sound:
• I/O ports:
  • All Commodore 64 ports with percent compatibility, plus the following:
  • Higher "burst mode" speed possible on the serial bus
  • Expansion port more flexibly programmable
  • RGBI video output (DE9-connector) logically similar to the IBM PCCGA connector, but with an added monochrome composite signal. This added signal causes a minor incompatibility with certain CGA monitors that can be rectified by removing pin 7 from the plug at one end of the connecting cable.
  • External keyboard input (DBconnector) (CD(CR) only)

See also[edit]

Notes[edit]

References[edit]

External links[edit]

Another Z80 on the system buss would load the initial program into ram and then release the Z80 Reset. 65 I went a little crazy with the hot glue, but as you can see, the only components are a 74HC used as an input port, a 74HC used as an output port, a few pull-up resistors for the SD card pins, and a capacitor for the supply voltage. With the ST interface, the drive was connected to a controller card with two cables and power. The ZSIO card adds bank-switchable RAM up to K, a real UART for faster serial I/O, and an SD-card interface to provide "disk" storage. There is no power switch on a Raspberry PI. I've only a few ideas right now, like using the SPI interface of an SD-card. I know that I can push the FAT filesystem support onto the Z80, but that would require substantial effort. Games in the file format TZX – a tape format used for preservation purposes – need to be saved on to an SD card and inserted into the ZX Spectrum Next. SPI SD Card Interface for Z80 Systems This web page documents a high-speed SPI interface I built for a Z80 system. In the config file on the SD card there is a file config. Since the cased Next's started to arrive in the hands of backers, software development has increased with new utilities and games arriving every week. All this is achieved by giving the PIC ultimate control over the Z80 by controlling the reset and clock lines, as well as the DMA control lines. Right now, a read command is issued by the Z80, the AVR reads the full bytes of data, and then sends bytes to the Z80, discarding the rest. This mostly affects SD card access where most of the time is spent transferring data between ATMega and Z80, with Z80 sitting in wait state, waiting for the ATMega to service the interrupt. We need six IO space addresses. As technology progressed, more of these functional units could be placed on a single card. From Brazil. Allows two cards but more importantly easy copying between them for cloning. TRS80 and ZX Spectrum Graphics. Updated S Z80 SBC page. FAP80 is a Homebrew Computer Built with Zilog Z80 CPU Designed over the course of a year dekuNukem built – twice! – this homemade ‘FAP80’ computer . 2 w/ SD CARD. First head into the "Z80asm" directory and type "make" to build the romsets. I'll be cheating heavily with that, getting the Teensy to do all of the FAT heavy lifting. com. The steps I followed to accomplish this: 1. I think that well implemented I2C bus devices, such as the PCA in DIP, would be a good place to start for modern interfacing on the RC Using the driver successfully requires a good understanding of SD cards and the FAT16/32 file system. I am trying to interface Atmega32 to SD card in SPI mode. I coded an SPI interface (one of the three spoken by typical SD cards) in VHDL that is able to wake up the card and download random byte blocks. Most of the z80 platforms in RomWBW support bit banged sd card interfaces and some of the z platforms use the clocked serial port of the z80 with alookup table to reverse the order of the bits. Important: SDO and SDI are the pin names from the SD-card point of view, i. N8VEM builders made their own homebrew computer systems for themselves and shared their experiences with other homebrew computer hobbyists. I designed it mainly as a low-cost, simple to use game loader and as such it features a Kempston compatible joystick interface, SD card slot and reset / NMI buttons. Z80 INT --> INT0 INT1, INT2 are extra interrupt lines, not needed yet. Enjoy! Source credits. If MREQ is low then the Z80 is trying to access RAM and if IORQ is low then the Z80 is trying to access an IO device. Controlling this is a simple emulator for the Disk II controller, which provides a very low-level interface to the drive. Most added a simple interface to improve communications with other Z80s. Z80 CTC; SD Card interface. 8/18/ Added description of SD Card Drive interface to FPGA Z80 SBC: 8/6/ First viewing of the S bus FPGA Z80 Single Board Computer: 6/22/ : Added complete TTY program example to V2 FPGA board for a VGA Jun 03, · It’s definitely possible, since it’s a Z80 with a file system interface (SD card). They would have to go to large memory chips via flying wires. My recommendation: go ahead and do it! Research, learn a lot along the way and have fun. The major improvementsSD card has a native host interface apart from the SPI mode for communicating with master devices. If you are using an SDHC memory card in a digital Camera Camcorder Video SD Secure Digital Card with very high megapixel rating or recording HD video we would recommend using a Class 10 card for optimal performance. works with the BBC B, B+ and Master. - connect it to a VGA monitor. Watch. We used the protoboard to develop the next board in Z80 Membership Card family. Onboard 5v->3v regulator provides mA for power-hungry cards3v level shifting means you can use this with ease on either 3v or 5v systemsUses a proper level shifting chip, not resistors: less hi, I am using LPC micro controller for interfacing with the SD card. 7. Credits for this manual: Giorgos Levas Guido Lehwalder Ed Spittles 1. Here is a simple USB interface to allow the Z80 to talk to a PC: With the ST interface, the drive was connected to a controller card with two cables and power. In addition it provides mass storage (via an SD card interface) and a useful in-circuit emulator for debugging. For Z80 you would need to find the software or translate from some existing software that works with a microcontroller interface You would need to add hardware to Z80, test it and get software working. The interface could also be interrupt driven but I don't see it as a problem if the Z80 ends up waiting on the SD card. Even the MCUs built into the screen and SD card are probably all more powerful. See the separate Minstrel ZXpand listing for full details or if you want the further options. 00 Vintage MPC Serial Interface Card for Apple II Computers - New Old Stock, Sealed You could also convert the N8VEM SBC RTC circuit (74LS & 74LS) to have 3. Raspberry Pi Zero will be instructed to load the game’s data from the SD card. The only thing you have to do is converting the TTL signal based serial interface into V24/RS voltage level, which can easily done by a small module with a MAXN chip (and a few capacitors). Class 10 SD memory cards are the fastest speed available and can cope with very large files without the risk of playback lag. ZX-Badaloc clone Also from Alessandro Poppi, this is not an interface for a standard Spectrum but a complete clone designed to fit into the rubber-key case. The source code I use is from Secure Digital Card Interface for the MSP Z80 CLK of Z80 --> EXTAL PHI is the CPU clock output. The OS kernel is the most cryptic part of the project, being reverse engineered from a firmware for the divMMC SD card interface, but source code is provided. Three SD card formats are available today: standard, high capacity, and extended capacity. Originally it has CF interface. with regards, Abhishek Dixit SD card interface and initialization Console port for ZChibiTerm connection, using UART at Heathkit H19 terminal emulation, with special key mappings for WordStar N8VEM was a homebrew computing project. This fits internally, plugging into the Z80 socket and supports two card slots. You can see that a file, and directory with the same file would have been created. Free shipping Interface Card. Specifics on these can easily be found on wikipedia's SD card page. Now you can run the CP/M operating system on the Z80 Membership Card! I am attempting to make a retro computer using a z80 and ideally would like to give it the ability to boot from an SD card. Since I have a few, I was planning to use an 82C51A UART and use an 82C55 as a simple parallel I/O device. The disk is still a lot faster than typical drives of the CP/M era, though. For the pins settings, see the section “Hardware environment” 3. 3V). But it’s a fun exercise. However I have used Arduino to test it is fine but I want to interface it with lua language. It looks at running a Z80 emulator on state of the art microcontroller hardware. And as for using the Z80 to address a particular memory location on the card… well, forget it!The first SD/MMC interface for the Spectrum, from Alessandro Poppi. It is called SD_CARD. Y: Jul 06, · For instance SD Cards could be used if you can replicate the SPI protocol via the Z80, or a compact flash card could be used in its regular mode by introducing some extra circuitry in the form of latches to account for the default bit mode ,but I want a much simpler interface. 3v Zener diode) and hook it directly to a SD card but that would be fairly major software development. 3. Possibly easier to Damage. Create switch routine in ram and switch to program. The version here is the one with the pin header which is soldered directly to the Minstrel 3 expansion connector. From this source code above, there is no process, when I debug and I could not send any user input to the SD card. DREQ1, TEND1 are for DMA which I can ignore for now. SDO needs to be connected to SDI on the microcontroller and SDI needs to be connected to SDO in BBC Micro SD Card Interface. keyboard), and this selection is made by driving MREQ or IORQ low (0V). The SBC-type cards plugged into either a standard slot or the aux slot. I modified the context switching mechanism to make it much more efficient by eliminating all the memory copying. Standard SD cards come in three physical packages: full sized, mini, and micro. 3V logic to interface to the pins. Sep 12, · Ive built the Z80 CP/M variant, complete with VGA & Keyboard terminal, Serial port, SD-Card and external SRAM. The drives were "dumb", because the control card had to translate requests for a particular track and sector from the host system into a sequence of head positioning commands, then read the signal from the drive head and recovered the data from it. - connect a parallel 40x2 LCD display directly to the Z80, so it can output text by itself - build or connect some kind of keyboard. The Serial SD Drive module is the mass storage module that I've created for my Z80 to interface with. txt. In this tutorial, the word SD Card will refer to SD, miniSD, microSD and SDHC. The video is In addition it provides mass storage (via an SD card interface) and a useful in-circuit emulator for debugging. The main question is how much work it would be to create a port. It is capable of transferring a byte in just 1 µs. However, the I2C path is also quite interesting. SPI SD Card Interface for Z80 Systems This web page documents a high-speed SPI interface I built for a Z80 system. Find out more Use the USB-SD card adapter to copy them onto the micro-SD card. Ultimately, it would be preferable to use an SDHC card since it's getting increasingly harder to find low capacity SD cards. STE-Z [Lee] has packed in a ton of features on the custom monitor ROM for the front panel card making it a The 74HC buffer (the same type I used in the video circuit) is used for data from the SD card to the Z when the Z80 issues an "IN" instruction it takes IORQ and RD both low, and the combination of both enables the ' output drivers, placing the MISO signal from the SD card onto the Z80 data bus. The cards generally operate the Z80 at MHz, but they do not have direct access to the Apple II hardware. RC is a simple 8 bit Z80 based modular computer originally built to run Microsoft BASIC. In early S bus systems, it was not unusual to find a Z80 CPU with bus interface on one card, and several memory cards with 64 static memory chips on each. I2C Port. Teensy Z80 – Part 3 – File System, SD Card, VRAM? Posted on January 18, by Domipheus This is the third part of a series of posts detailing steps required to get a simple Z80 based computer running, facilitated by a Teensy microcontroller. info/z80core4. Again, this is a standard S bus program that can be downloaded from your PC via the FPGA monitors "X" command. Since the SPI is a widely used protocol and it is available in most low-cost microcontrollers Get the best deals on Z80 Indiana Vintage Computer Parts & Accessories and find everything you'll need to improve your home office setup at eBay. Interfacing a Z80 to an SD card isn't totally straightforward though. Z80MC Serial/RAM/SD-Card. Using and testing each core . SD card and perform directory operations. The native interface uses four lines for data transfer where the microcontroller has SD card controller module and it needs separate license to use it. The major improvements Apple High Speed Serial Interface Card x Guaranteed to work fine . htm. - Kempston Mouse Turbo interface - ZX-HD HDMI interface - ZX-AY external audio interface In the box Your DivMMC EnJOY! PRO MINI interface is delivered with an SD card and this manual. Slot-Based (][+, //e, IIgs) The simplest user Z80 was a Z80 card with memory that plugged into a system buss. g. Short for FPGA Assisted Processor, FAP was originally designed with numerous through-hole components on breadboard and perfboard (below, left) before being redesigned with SMT and custom PCBs. MOSTEK MKP-4, 4Mhz SIO SD card interface PCMCIA interface. I've already got Mode 2 interrupts working, and I'm interfacing an SD card interface. Adapted the pinouts, ports and some signals of all the modules (Main Interconect, Z80, VGA, Serial, Keyboard, SD-Card) from the original d Hi there, just out of curiosity, I am currently in the middle of building my own SD card interface for my enhanced IIe. Jul 21, · For quick SD Card interface, in your position I would want a working CP/M system if at all possible first. It provides a great way to move files to and from the Z 5. The card has nine pins, as shown in the figure 2 below, and a write-protect switch to enable/disable writing onto the card. It is not a clone of anything specific, but there are suggestions of the ZX81, UK, S, Superboard II and Apple I in here. I'm posting the code I've written to read from, and write to, the uDrive from the Z80, as well as display the contents (sort of a directory, but not nearly as fully featured) of the micro SD card. 26 watching. Jun 23, · Z80 computer with new SD card slot (bottom left) and real-time clock (top right) CP/M consists of three main pieces of software: A BIOS which exposes a small number of routines to perform primitive, hardware-specific operations (e. 64k RAM, switchable ROM, SD card interface; Arduino-based SD drive; rcSB/ ROM/RAM switcher system; Build info. 6) Once the example project has been completed remove the SDcard and connect it to the PC. That's µDRIVE-uSD by 4D Systems which combines a micro-SD card socket with a tiny tiny microcontoller on a board for US. This is an SD card reader and joystick interface. Make sure this fits by entering your model number. This is awesome. z EPSON Interface Card for LocalTalk - Model C - Apple Macintosh Apple IIe 80COL/64K MEMORY EXPANSION CARD P/N: SD card interface and initialization Console port for ZChibiTerm connection, using UART at Heathkit H19 terminal emulation, with special key mappings for WordStar. A game can then be selected via the Next computer’s built-in Browser mode. Adding The SD Card Interface. If you do need to turn it off, there is a shutdown feature in the web admin interface provided by TIPI. RubyUI UESP(Uno/ESP) is a text-based user interface, than is supposed to be launched on the NodeMCU 12E/Arduino Uno, and has a purpose of processing SD card files or basic text apps, integrated into functions, such as a calculator or even a text based game. ; SanDisk 8GB Ultra 15MB/s SDHC SD Class 4 Memory Card (SDSDHG-P36) for Casio Exilim EX-FC, EX-FC, EX-FH25, EX-FS10, EX-H10, EX-H15, EX-S10, EX-S12, EX-S5, EX-S6, EX-S7, EX-S, EX-S8, EX-S, EX-V7, EX-V7SR, EX-V8, EX-V8SR, EX-Z, EX-Z, EX-Z, EX-Z, EX-Z11, EX-Z, EX-Z, EX-Z, EX-Z, EX-Z, EX-Z, EX-Z29 USB library, HID keyboard interface; MMD File System with SD card interface; Graphics library (v2. It also appears that the ram for the Z80 is coming out of the 64KB built into the M4. It is able to load files from the SD into the Z80 RAM memory, show bitmaps files and run binary files. After issuing a shutdown, wait for the PI's sd-card activity light to stay off for 10 seconds, then pull the power. You should consider leaving the Raspberry PI always on. This port can only act as an I2C bus master and does not support other bus masters being connected to it. The card is formatted and contains some ZX Spectrum software for you to try instantly when you use your DivMMC EnJOY! If you want pure a SPI interface (pure meaning without introducing another CPU augment the Z80), then this looks to me like the best option. Project’s official wiki page. Secondly, there are two ways to interface with SD cards - SPI mode and SDIO mode. It is inspired by the home built computers of the late 70s and computer revolution of the early 80s. Z (2. The long term goal is to replace the current FPGA core with a dedicated bit core that will provide a number of additional features. You will find the layout as is processes here. Jan 09, · With this, we have a display, serial in/out, and can now try writing some more z80 ASM! But for now I think this is enough for this part. Wednesday, 23rd June 0) These four components are then customized to provide emulation of the specific hardware features of the (Timex/Sinclair) ZX Spectrum personal computer. I am % set on using a z80 and do not want to use a microcontroller with an internal SPI hardware interface. info This is the 3rd video of my Home made Z80 computer. It featured a variety of free and open hardware and software. It starts in RAM at H. Secondly you must also have 3. 9/4/ Final description of S bus Z80 Single Board computer. Brand: Unbranded. and SD_POW_EN are used for interface to the SD card slot. SD cards come in two popular flavors - microSD The Serial SD Drive module is the mass storage module that I've created for my Z80 to interface with. Extra joystick ports are nice too (usb interface would be fine for space saving) I have the Enjoy! Pro 1 and the ZXHD and it works well together, but I think it looks a bit ugly and unstable together. The Z80 Minicom II is a redesigned and improved version of the Z80 Minicom with the ability to use the entire 64K RAM space by switching the ROM out and with the addition of a CompactFlash card it has permanent storage, allowing it to run CP/M 2. For past 4 weeks I been trying every possible methods mentioned in different forums and SD card datasheet. Next, go into the "rc" directory and type "make" to build the emulator. This is SD card interface for Grant Searle's CP/M computer. More info at: http://www. Apr 06, · Schematics at: http://www. PiTubeDirect Readme. . RC is a simple 8 bit Z80 based modular computer originally built to run Microsoft BASIC. Specifically, a Grand Central M4 Express. I have his permission to redistribute this software as part of my work. Mar 15, · It is now with video output (ntsc), Keyboard (ps2) and SD Card Interface (spi). It's definitely possible, since it's a Z80 with a file system interface (SD card). 00 Interface Card. 5) Press Reset button (SW1) of the kit and check the messages displayed on the COMPORT terminal. from TFW8b price: 30 GBP platforms: BBC. Booting CP/M 3 from an SD card. Most microcontrollers have extremely limited built-in storage. The pins on the connector SV1 need to be connected to the microcontroller pins. To simplify and reduce “glue-logic” gate count, I would dust off my CUPL skills from a decade or so ago and make use of some LATTICE GAL20V8Z SPLD’s I still had from when I worked N8VEM was a homebrew computing project. PiTube official releases. Instead, every SD card has a 'lower speed' SPI mode that is easy for any microcontroller to use. Nice to know it has been done and even better if it can be utilised. Figure 2: SD Card pins. I’ll be cheating heavily with that, getting the Teensy to do all of the FAT heavy lifting. One Z80 chip, two propeller chips, VGA, TV, SD card, touchscreen, k ram, I2C port, keyboard, audio. The PSoC SD Card Driver. I lifted the serial port part…. Standardised access to real-time clock for file date and time stamping. Pins suitable for the breakout board I have. Get the best deals on Z80 Indiana Vintage Computer Parts & Accessories Z80 ZETA V2 SBC Single Board Computer CPM For the Arduino, however, only the SPI mode can be used. The tricky part for me, right now. Touchscreens are great for graphics but they are a bit tricky in that they need fast data transfer to be able to refresh a screen of text or move sprites Mar 31, · I will post the schematic it’s pretty straight forward “lifted” from my Buddy Josh Bensadon’s JAIR board which includes , ram, dual serial ports, parallel port, and SD card interface for 4 drive CP/M system, all in one card. Other features: Kempston joystick interface Reset button Enable/disable boot ROM. but i am unable to interface SDcard with LPC The BusRaider 2 is an add-on card kit for the RC retro computer which adds memory-mapped graphics, connectivity via WiFi, a web user-interface and single-step debugging. Here the schematic of the SD-Card module with the voltage level translation. output a character to the console, read a raw sector from a disk, check if a key has been pressed). But still no success. But it's a fun exercise. Note: in earlier versions of the scheme UM 5 and UM 2 was connected to U I2C Port Adafruit Industries, Unique & fun DIY electronics and kits MicroSD card breakout board+ ID: - Not just a simple breakout board, this microSD adapter goes the extra mile - designed for ease of use. The Front Panel Card has a key hex pad, 7-digit 7-segment LED display and Serial port. 2) second SD Card interface. The aim of this little project is to try to extend CP/M so it runs on a touchscreen. SD mode rearranges some pins and uses all of them. Bytes are transferred through the interface with this simple assembly code:Z80MC Serial/RAM/SD-Card. It probably won't take much effort to port your hardware interface into RomWBW and take advantage of the existing protocol software in RomWBW. Read menu for SD card as present to user with choose to select program or jump to native machine. - Sun Jan 17, pm # Hello, I want to interface sd card with in lua language but I did not get any promising example. Add copro=NN where NN is the number of the CoProcessor. Implementation This section introduces how to access a SD card with the SD/MMC interface on LPCxx devices based on FATFS. Corrected. Also, you need a serial interface to connect to your computer. Early static memory was 1k by 1 >bit per chip, so one of these cards was 8k bytes of memory SD-Card Module. Get the best deals on Vintage Computer Interface Cards for Apple and find everything you'll need to improve your home office setup at eBay. The byte block from the SD card can be read by the PSoC into a receive block. For example, even the Arduino Mega chip (the Atmega) has a mere 4Kbytes of EEPROM storage. -A DMA to transfer from the SD card to memory at 10x the speed? Play PCM samples? Transfer to the VDP?-What if that Z80/R cpu had hardware division? Or floating point?-What if running z80 code it could be as fast as a Pentium ?-Longer buffers for the MIDI interface, maybe using the DMA as well for buffering. Or maybe it is out there somewhere on the web. Instead, every SD card has a 'lower speed' SPI mode that is easy for any SD card interface and initialization Console port for ZChibiTerm connection, using UART at Heathkit H19 terminal emulation, with special key mappings for WordStar 4) Insert an empty SD card (upto 2GB size). 2 It also uses an ATmega microcontroller to drastically enhance its IO potential: Hello, I've finally got my z80 homebrew machine going its only 25 years since I first wanted to build one! At the moment its very simple but I'd like to (try to) interface it to a 's VGA card. Instructions to Load/Run Quartus. Demo of the project on youtube. I’ve already got Mode 2 interrupts working, and I’m interfacing an SD card interface. Just as importantly, it has an onboard SD card slot which is needed The default SD card position is P2, SPI SD Card 1. Typically, 4-bit mode of SD interface is used to access a SD card with a single voltage (3. If it has a traditional RS serial port, you're all set! Build the ZSIO card with the RS option. Since the SPI is a widely used protocol and it is available in most low-cost microcontrollers, the SPI mode is the widely used interface in low cost embedded systems. Load file to memory from SD card 4. I ported the kernel to ANSI C and made it build with the modern SDCC compiler, added drivers for my MMU, UART, RAM disk, an SD card interface, and removed the Z instructions. The first SD/MMC interface for the Spectrum, from Alessandro Poppi. I went a little crazy with the hot glue, but as you can see, the only components are a 74HC used as an input port, a 74HC used as an output port, a few pull-up resistors for the SD card pins, and a capacitor for the supply voltage. Supplied with a ROM containing Smart SPI but should work with other BBC SD and MMC card ROMs. The SPI mode only uses pins , leaving off the small one and the recessed one (8 and 9). Now you can run the CP/M operating system on the Z80 Membership Card!CP/M running, with maxed out storage on SD card (16x8MB drives). This is the easiest way to get your initial CP/M programs and data into your Z80MC. Note: both the keyboard controller a few posts back and this circuit have no address With this, we have a display, serial in/out, and can now try writing some more z80 ASM! But for now I think this is enough for this part. SD Card Pin Configuration. You need at least MB card. This project Click to download the latest Firmware, ROMS and Documentation The SMART Card is an expansion board for the Sinclair ZX Spectrum. I want to understand both the hardware and software aspects of a computer, so arduinos and microcontrollers are It is now with video output (ntsc), Keyboard (ps2) and SD Card Interface (spi). . The motherboard has a bit-bang I2C bus port. SPI mode requires four pins (we'll discuss them in detail later) so it's not pin-heavy like some parallel-interface components. Many of the popular Z80 computers of the s and s used a region of memory to produce graphics (either character-mapped or bit-mapped). We have enough information now to start to design the PSoC low level software for the SD card interface between the Z80 and the PSoC. Just to be clear here: yes, he is using a bit 72 MHz Cortex M4 and a 12 MHz Cortex M0 as an IO controller for an 8-bit 8MHz cpu. The Z80 can access either RAM (memory) or IO devices (e. I am not trying to build a floppy replacement, but more of a ProFile replacement with a SD card with one (later multiple) 32MB ProDos partitions. javascript:emoticon(':(') The card is not responding when I send the CMD55 and ACMD41, no matter how many times I repeated the routine. If RD is low then the Z80 is trying to read from that selected device and if WR is low then the SD cards are possible in theory, but quite a pain - they use a 3V serial interface, and the Z80 is based around 5V parallel interfaces, so you'd need to do level shifting and use software "bit-banging" to implement the SPI protocol, which would make things quite slow (although still a lot faster than an old tape drive!). An SD card has two modes, SD and SPI. Interfacing a Z80 to an SD card isn’t totally straightforward though. SDIO mode is faster, but is more complex and as far as we can tell, requires signing non-disclosure documents. 2 on the Z80 computer. And can be downloaded at the bottom of this page. For debugging, how could I send data to the SD card? The data should be received from the ADC12MEM registers and just need to be written in the SD card. This board is built around the SAMD51 MCU which has plenty of memory and power to run an emulator in real time. I instead decided to go with the model where I have a smart serial-based device that you tell it "i want this file" and it sends it out. And as for using the Z80 to address a particular memory location on the card… well, forget it! There's an on board microSD memory card interface and adapter, which supports microSD cards up to 2GB - that's a lot of space for CP/M computer indeed. Fortunately the code exists (Juha's work on the N8VEM SBC SD interface) but it would still be a big project. Fast & Free Z80 ZETA V2 SBC Single Board Computer CPM 2. The second connector could also be used for any SPI peripheral with suitable software. For starters, the Z80 runs on an 8 bit parallel data bus, but SD cards use a Serial Peripheral Interface (SPI). Z80, You need software & hardware. (Now on Pin 14) Fotos here Licence I use some code from Grant Searle. . I have an old ISA VGA card (pictured) it's marked "CT Magic VGA" and uses the "Cirrus Logic GDA" chip-set. ATMegaP as system controller: Provides system clock for Z80; Contains and serves bootloader, monitor, and CP/M binaries; At startup, patches Z80 bootloader into first bytes of RAM; SD card interface and initializationI am attempting to make a retro computer using a z80 and ideally would like to give it the ability to boot from an SD card