Following on from my "advanced notice" post, I now have pleasure in announcing the "Multicomp" design-your-own computer is now online.
*****UPDATE 6th NOV 2019 - NEW HOSTING AND DOMAIN - PLEASE GO TO http://searle.wales AND FOLLOW THE LINK FROM THAT PAGE*****http://searle.hostei.com/grant/Multicomp/ (NOW DEAD)
[ TEMPORARY MIRROR : http://zx80.netai.net/grant/Multicomp/index.html ]You can build a 6502, 6809 or Z80 computer with internal or external RAM, connected to a TV (composite video or RGB) or VGA monitor or to a serial port, or both.
The entry can be either using a serial port or a standard PC PS2 keyboard.
External memory available to the built-in BASIC goes up to 56K using a single SRAM chip. Internal memory is 1K to 4K depending on what you choose and how many characters you have on the screen, if you are using one.
The video output is either monochrome on a standard composite video out or 16 colour RGB foreground/background (colours set using the standard ANSI code sequence) for each character or for the whole screen (lower memory).
Speeds of the internal CPUs run at up to 25MHz (internal RAM) (yes, really 25x the speed of a normal 6502!) or up to 10x or more with external SRAM (can achieve 25x with fast external SRAM).
Grab it and have a go - if you have already done my UK101 FPGA build then the same hardware and wiring is used - no changes needed.
If you try and get stuck, please contact me (see eMail link on bottom of web page) or feedback on this forum. All feedback welcome.
You can send me your VHDL and a summary of what you were trying and I'll get it working for you if needed.
Anyway, have fun - there's a lot of info on that page, but it is all step-by-step.
I have re-tested it today with the following computer builds, all working. These are just a FEW examples of the builds that you can do with the code that I have provided...NO ADDITIONAL CHIPS (ALL INTERNAL TO THE FPGA)6502 processor, 2K internal RAM, 40x25 full colour on a PAL monitor, PS2 keyboard
6809 processor, 2K internal RAM, 40x25 full colour on a PAL monitor, PS2 keyboard
6502 processor, 1K internal RAM, 40x25 full colour on a PAL monitor, PS2 keyboard
Z80 processor, 2K internal RAM, 40x25 full colour on a PAL monitor, PS2 keyboard
Z80 processor, 1K internal RAM, 40x25 full colour on a PAL monitor, PS2 keyboard
Z80 processor, 4K internal RAM, serial interface for I/O at 115200 baud
Z80 processor, 2K internal SRAM, 40x25 VGA monitor full colour display, PS2 keyboard
ONE ADDITIONAL SRAM CHIP6502 processor, 8K external SRAM, 80x25 VGA monitor full colour display, PS2 keyboard
6502 processor, 32K external SRAM, 80x25 VGA monitor full colour display, PS2 keyboard
Z80 processor, 32K external SRAM, 80x25 VGA monitor full colour display, PS2 keyboard
The display does not have to be 40 or 80 chars, nor 25 lines - set it to whatever you need. On the page I have an example for 68x30 on a VGA screen (if you turn off the colour attribute option then again it can all fit within an FPGA with 2K program RAM internal - no additional chips needed).
Google ANSI colour (color) sequences to see how to set colours
As an example, to change the text colour in BASIC...
PRINT CHR$(27);"[92m"
Will set the foreground of characters that will be printed to bright green.
PRINT CHR$(27);"[44;93m"
Will set the foreground of characters that will be printed to bright yellow and the background to normal blue.Have fun, as always.
Regards.
Grant
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