Hi all

I've mailed Grant but I thought I'd ask here too.

Today I attempted to build a Multicomp (http://searle.hostei.com/grant/Multicomp/index.html?mmskip=1) after waiting weeks for the parts to arrive from China.

I wired the board with a single serial port, external SRAM and an SD card.

I installed the Altera Quartus software (what a palaver!), loaded the USB Blaster driver and opened the "Microcomputer.vdl" file. I configured it as a Z80 machine with full external SRAM, single serial port and SD card (basically, per the hardware setup). I finally got the thing to program the board but nothing happened. The programmer is set for the correct board. I noticed that each time I power cycled the board the three LEDs next to the JTAG header flashed at about once a second. Reprogramming the board seems to make the flashing stop. Does this mean that the board really isn't being programmed properly?

Anyway, suspecting a problem with the physical wiring, I went back into the VHDL and reconfigured, this time for a serial port and 4k internal RAM. In this mode, only the serial port is connected and active, so any wiring errors should be irrelevant. Naturally I checked the serial wiring again. Ran the programmer but nothing on the serial port at all. Swapped RXD / TXD but again nothing.

Trying with a different rs232 converter board which has LEDs on it, I noticed TXD was constantly on, and occasionally the PC reports that it cannot connect to the port. Something is definitely wrong.

The last thing I have tried us to lower all the clock speeds. CPU at 1mhz, serial at 9600 baud, still nothing.

I'm concerned though, because the setup seems to have a CTS line (no RTS) but my serial - TTL board only has TXD RXD GND PWR. No hardware handshaking at all. Maybe the port is waiting for CTS? I have tried connecting it to Vcc (asserts CTS all the time) and GND (because it is really !CTS) but neither work.

So I'm a bit stuck now and hoping for advice. My money is on the "programming the board" bit as the Altus software is complex and I am new to it. Tomorrow I will disconnect the SD card and SRAM, cut it back to the basics, but I'm pretty sure it won't make any difference.

Is there a way to test it?

Cheers
JonB

Turned out the pin assignments had got lost in one of the files, so Quartus was assigning them randomly.

Got this sorted and now I have a spider on my desk.

Ports from top left: VGA, PS/2 kbd, SD card, Serial 1, Serial 2. Haven't tested it yet....

Congratulations

Wich SRAM are you using and how fast is the board running?

I have made 3 versions of this as Z80 running CP/M

One exactly as Grant have designed it on Cyclone II, one on Cyclone IV and one on Xilinx Spartan 6.

The Spartan 6 version have 64KB internal RAM and running at 135MHz

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Jens

Welcome JensEP! Those blue boards look good, are they your own design or commercial?

If you like high performance for your Z80 core, you might see if you can swap out the T80 core for a NextZ80 core - it might not clock quite as fast but it uses fewer clocks for each instruction. See
http://stardot.org.uk/forums/viewtopic. ... 01#p106301

Cheers
Ed

They are from China:
http://www.ebay.com/itm/Cyclone-IV-FPGA-Board-EP4CE6E22C8N-EP4CE6-Development-kit-CPLD-ALTERA-PLD-NiosII-/281188502846

http://www.ebay.com/itm/XILINX-Spartan-6-XC6SLX9-FPGA-Developement-Board-Vivado-ISE-CPLD-SOC-MicroBlaze-/231092874536

and I just found another Spartan 6 board:

http://www.ebay.com/itm/Xilinx-XC6SLX9-Spartan-6-FPGA-Core-Board-Nano-Size-/111640406811
This one is cheaper and have FTDI onboard (original hopefully).

...and a new Cyclone IV board:
http://www.ebay.com/itm/Altera-EP4CE6-Mini-Board-Cyclone-IV-FPGA-/111621868286

I will look at the NextZ80, thank you.

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Jens

Thanks for the links!

Hi Jens

It is exactly as specified on Grant's site (uses the AS6C1008 as pictured) and it runs at 25Mhz which is fast enough (for now) given the limitations of the serial interface.

I would be very interested to see details of your board and VHDL. What I really wanted was something even faster (like what you made with the Spartan 6).

Regards
JonB