This page is intended to document the current state of play for non Z80 based systems using RC2014 and related compatible hardware.
RC2014 is defined by its creator and trademark holder not just as a bus design but as a Z80 based system with a 7.3728MHz clock. Whilst the bus itself is very much the Z80 CPU bus extended this doesn't mean it can't be used for other things, any more than S100 was limited to the 8080.
The first variations have been to the clock, with Z180 boards running at 18MHz or similar clock rates. That in and of itself creates incompatibilities with some boards. The Z180 also needs part of the I/O space for internal peripherals which in turn created more limitations.
Using other processors raises further challenges. The Z80 peripheral chips that are commonly used for the serial interface, and sometimes for timers and general purpose I/O are not compatible with other processors without fairly serious additional magic. The original RC2014 uses a 68B50 for the serial interface which (if correctly decoded) is compatible with other processors - and indeed was not designed for Z80 bus in the first place. The later serial design uses the Z80 SIO which is not compatible.
Providing they can meet the timings most other RC2014 peripheral cards and memory cards appear to be compatible with non Z80 processor systems. This is not as simple as a straight forward clock speed comparison because some processors expect to perform a whole bus operation in a single cycle unlike the Z80. A 6502 at 2MHz is for example roughly as demanding as a Z80 at 8MHz.
The 1802 processor card supports the CDP1802 and equivalent processors. It should work with the 1805/6 as well but this has not been tested. A test ROM image that implements SCRT and prints Hello world on a 16x50 UART card is available but as yet nobody has ported ElfOS.
The 6303 processor card supports the 6303 and 6303RP variants of the Hitachi 6303 processor, which is slightly pipelined and improved version of the Motorola 6803. It requires a standard RC2014 memory card and clock (7.3728MHz) for a 2MHz 6303 part, or half that for a 1MHz part. The onboard serial port and GPIO lines are accessible. The memory card must be able to put ROM at the top of the memory space. The 32K RAM/32K ROM card is ideal for this or the 512K banked memory card can be used.
Because this board uses standard RC2014 clocks it works with most of the existing hardware tested so far, except as expected the Z80 peripheral chip based cards. The CPU runs at 1.8MHz which means that the other timing requirements look much like the Z80 card. The M1 signal is however not supported and pulled high. The Z80 I/O space is mapped to $FE00-$FEFF in memory.
Software support includes a boot ROM and Fuzix OS.
An earlier design for RC2014 can also be found here.
The current 65C02 card supports classic but not modern WDC 65C02 parts. There is an onboard clock socket so only memory and serial I/O cards are required in order to use the system. The memory card must be able to put ROM at the top of memory space. The 32K RAM/32K ROM card or 512K banked memory card can be used. The original card mapped the I/O at $C000-$C0FF which causes problems for some software. The current board design uses $FE00-$FEFF so some software may need to be modified to use it. The M1 signal is not generated but pulled high. The 65C02 E clock is used as CLK and RW is optionally available on a user pin so that 65xx peripheral cards can be used.
It works reliably with most of the RC2014 cards at 2MHz but not all of them at 4MHz or higher, where the timings become much more demanding than the Z80 at standard RC2014 speeds.
Software support includes BASIC, Monitors and Fuzix. The software and boot ROMs are mostly built to support a 16C550 type serial port at 0xC0.
Version 3 of the board which should support the problematic WDC parts is built and pending testing. It also adds the hooks for an experimental 'protected mode' MMU card.
This is designed to be RC2014 compatible and drop into the 65C02 board slot without software changes. It therefore does not use the 24bit addressing but can run with 16bit addressing and the standard RC2014 banked memory cards.
The 6803 should work with the 6303 board and a wire link. This needs testing but there is no specific plan for a 6803 board. The same ROM firmware will be able to run with both processors.
This CPU card supports the 6808 processor (not the 68HC08 which is not the same thing at all). As with the other Motorola style bus cards the E clock and RW are available on user pins.
Ben Chong designed a 6809 processor card for RC2014 and also some initial firmware. The new RC2014 card takes a similar approach but provides the same layout as the other Motorola bus CPU cards including the E and RW lines and placing the I/O at $FExx.
As the 6809 is an NMOS component care is needed that all the other cards on the bus are using 74HCT or similar and not 74LS/74ALS components. The 6309 should also work. The 6809E/6309E will not as they need different clock arrangements.
T68KRC is a 68000 SBC that has a limited RC2014 bus interface and runs CP/M 68K. All the essential I/O is on the board itself as are the clocks and memory. RC2014 I/O (but not memory based) peripherals can be used if desired.
The 68008 processor card provides a 68008 CPU interfaced to the extended 80pin bus and is designed to run with standard RC2014/BP80 cards including the 512K/512K linear memory card.
This card is currently being debugged.
A board for the 68HC11E series processors. This is much the same as the 6303 processor card except that the 68HC11 has more I/O options and can have on-chip ROM or EEROM. The serial, SPI, a pair of GPIO and Port E are brought out as I/O lines. The card can be built with an 80pin connector and drive A16-A19 directly.
This card supports the Fuzix OS, and it should be possible to port Flex and other more conventional 68HC11 environments to it, or run BASIC.
An experimenters board for using RC2014 from an 8052 or similar device with some internal ROM. Some of the Z80 control signals are jumpered so they can be driven in software from the internal ROM code to generate the relevant Z80 control signals.
The 80C85 processor card supports 80C85 processors up to 8MHz and has been tested with the Tundra 8MHz part which is the fastest 80C85 generally available. The board provides the clock, demultiplexes the CPU busses and provides the needed conversions for signals except M1. It also provides an optional MMU so that a flat 512K RAM/512K ROM BP80 memory card (as used on the Z180 systems) can be used. One oddity is that because the IRQ line on the 80C85 expects 8080 behaviour where the bus provides an instruction to execute all interrupts are taken via the 80C85 specific additional interrupt pins.
At lower speeds the board can be used with pretty much all of the RC2014 peripheral cards except those using Z80 peripheral chips. At 8MHz the CF adapter is not reliable. The PPIDE adapter is reliable as an alternative and the onboard MMU is designed to be used with the much cheaper and simpler flat BP80 memory card.
Software support includes boot firmware, CP/M 3 and Fuzix. All three expect a 68B50 or 16C550A based UART card, IDE CF or PPIDE and the flat memory configuration. The boot ROM autodetects the IDE and UART.
Board debugging in progress.
An initial hand built TMS9995 RC2014 board has been done by Chris Swan.
This board supports the Z8 processor with external memory. It provides the onboard serial and I/O port connectors as well as RC2014. The RC2014 I/O v memory is controlled in part by an I/O pin so a 32K I/O space is available. The data/code indicator is also available but not supported by any existing memory cards.
A boot ROM is available which can load code from CF card.
This board provides a dual 16550A port with proper baud rate control and which is compatible with all sorts of processors not just the Z80. It also provides much better functionality than the Z80 SIO or 68B50 having a much bigger FIFO.
For small configurations such as BASIC this board provides 32K of RAM and 32K of (E)EPROM. Most importantly it can be jumpered to place either ROM or RAM high so works with all processor types. Unlike some of the 'classic' RC2014 boards it also supports 28C256 EEPROM making it generally useful for development work.
This board is specific to the 65C02 system as it relies upon having the 65C02 RW line on a user pin. It might be possible to make it work with the 6303 board but the 6303 has onboard timers and GPIO of its own.
A board which provides timer interrupts for the non Z80 platforms. It offers an alternative to the Z80 CTC for things like Fuzix or MP/M that require an internal timer. For the 65C02 use the 6522 VIA board.
This board interfaces IDE disks and CF cards via a 16bit interface driven using an 82C55 so that proper signals and timing can be generated reliably with all processors (unlike the simple CF adapter). It is slightly slower but a lot more reliable. It can also be used as a general purpose digital I/O interface with all processors instead of the Z80 PIO based cards.
Note: although originally a third party board this kit is available from RFC2795 ltd having been adopted as a standard board although the RFC2795 one lacks some jumpers needed for using it for mode 1 and mode 2 I/O operation.
This board provides 8bits of digital input and 8bits of digital output in a form that is usable by any processor. It is not a direct replacement for the Z80 PIO in all cases as the Z80 PIO also supports interrupts.
These chips expect particular patterns of behaviour from the Z80 processor. They will not work at all with non Z80 parts on RC2014. For non Z80 systems without onboard serial the 16550A module is generally the best option, but 68B50 based serial also works. For PIO the SC129 digital I/O works, the 82C55 based PPIDE can also be used for PIO instead of IDE. If no internal timers are present and one is needed then the CTC can be replaced with the Intel 8253 card or the TMS9918A graphics can also provides a 60Hz interrupt. The 6502 board provides RW and E clocks to allow a 6522 to be used with it to provide PIO and timers.
These cards uses the full 16bit I/O address space of the Z80 processor. None of the non Z80 cards currently support mapping anything but the classic 8080 I/O space.
This interface is a hack on the Z80 and even on the Z80 only works with some cards as the timings generated are not within specification. When you use non Z80 parts this remains the same but the timing change so different cards may work. The CF adapter is known not to be reliable with the 80C85 at 8MHz and may be problematic with some 6502 processors.
These boards rely upon the Z80 bus control signals to take the bus from the Z80 processor. None of the other CPU cards support these extended signals
This is a list of other boards that have been tested and made to work with at least one non Z80 CPU card. This isn't a full validation test but just some general guidance as to what is likely to work.
This list does not include interfaces that attach to the serial rx/tx on the RC2014 bus, nor does it include backplanes and breakout boards. These are all processor independent.