6502.org

Hi.
The "multicomp" page is nearing completion (and lots of testing going on).

I have uploaded the current draft - not complete but will allow you to see the idea.
http://searle.hostei.com/grant/Multicomp/



The full expanded wiring is shown below but only a small part is needed for the simpler configurations.
Fully compatible with the UK101 wiring, so no changes needed if you have done the UK101

(All diagrams hand-drawn - no clip-art used)





Regards.

Grant.

http://searle.hostei.com/grant/

Hi

Sorry to resurrect an old thread, but... can I use a 64k SRAM chip with this? I have a spare HM6264LP-15 here and I want to build the full-on CP/M machine.

Cheers
JonB

PS, I salute you, Grant!

The 6264 is 64 kilobits arranged as 8 kilobytes. It won't do you much good for building a full CP/M machine (unless you use 8 of those chips).

If it's not for CP/M then the 64kbit (8Kbyte) chip is fine.
Connect all of the address lines that are available on the chip - don't worry about the top addresses (a15, a14 and a13) mentioned on the board pinout - leave them disconnected.

Then, follow the instructions on my page for using the 8K RAM option. I have tested this previously and it works fine.

All the best.

Grant
http://searle.hostei.com/grant/

Ah ok, I will have to get the right SRAM. It's for CP/M so I will need 64k.

I should have checked the data sheet before asking the dumb question.. D'oh!

Meanwhile, the kit is on order. The board was £7.50 and I the the programmer was £8. Another tenner for various bits (SD card holder, jumper connectors, breakout boards, plugs, etc) and I should be good to go. It must be quite fast in operation; that's what I am looking forward to.

I suppose I will have to get rid of a load of old Z80 computers once I have got this little beauty going.

I would like a 25mhz CP/M machine; is the proposed SRAM (Alliance Memory AS6C1008) fast enough? It's 55ms. Also what length patch wires can I get away with at 25Mhz (ordered 4" for the time being)?

If not can anyone suggest a fast enough alternative?

Also, I want to change the font for the VGA display. I take it this is just a matter of editing the font rom. True?

Thanks
JonB

Gosh. Exciting. It's all on order save the SRAM. Reminds me of the time I built Grant's MicroUK101!

EDIT: Another question just came to mind. Grant has supplied a pretty nifty means of bulk transferring files to the VHDL CP/M computer using DOWNLOAD.COM. Would I be correct in saying this would work on any CP/M computer?

Hi.
Been a while since I checked the calculations, but the ram on the page is fine. I'd need to dig out the timings but from what I recall there was sufficient time between the selection and the read / write due th the Z80 requiring multiple clocks for each operation.
The wires I used are about 4 inches long with no issues. Not tried any longer ones to see if they work, I'm afraid.

The font is a straight transfer from the CGA "bold" font. Any 8x8 font can be used, though just by replacing the hex codes, and with a bit of work other font matrix sizes could be used.

Glad you remember building the microUK101

Thanks for the comments on the downloader. It uses all standard CP/M 2.2 BDOS calls so would work on other CP/M machines if serial hardware handshake is available (which it should be anyway). If it's to go on an 8080 (not a Z80) they you need to check if any of my code uses Z80-specific opcodes - if so a minor change may be needed, but I don't recall using any. Source code online so feel free to use as you see fit.

Have fun!

Grant

I've had some great fun recently building all of Grant's wonderful designs. A real nostalgia trip for our generation brought up on MK14s, ZX80/81s, Spectrums, UK101s and VIC20s. My favourite MCU has always been the 6502...its in my blood and I remember OpCodes instinctively!! Bit sad really. Anyway I just wanted to mention that I bought one of these recently:- 'Cyclone IV FPGA Board EP4CE6E22C8N EP4CE6 Development kit CPLD ALTERA PLD NiosII' from Ebay. It has so much more memory and I have been able to not only use 16kb Ram but also implement Exmon in ROM. There is one snag which took me ages to sort out:- it is clocked at 25Mhz not 50Mhz. As you might guess it meant changing video timing and serial port timing to get it working but through trial and error I have it up and running beautifully. I knew nothing about FPGAs until Grant enticed me with his great instructions.What next oh great one !!

Very cool stuff. Yes, thanks to Grant's write-up I have also taken the plunge. I picked up the same board that Grant suggests (around $16 from China) and I've expanded it a bit. I've got a 512KB SRAM (AS6C4008-55) hooked up and I've created an MMU with VHDL. I'm able to run the CPU core at 16 MHz with that RAM chip but I'm hoping to try a 10ns RAM soon. I've also replaced the 8K BASIC ROM with a 1K monitor ROM and I've got a monitor that I've had for years that runs great and just takes up a little space around $FC00-FFFF. Shuffled the I/O address around and in addition to the PS/2 port and VGA I've also got a serial port. My monitor will accept Motorola S19 records which is what my assembler creates. So after I run the cross-assembler on my PC I simply squirt the S-record file out a serial port on the PC into the Multicomp and the code is loaded quickly and easily. I can do debugging and stuff in the monitor from my keyboard and the VGA display.