• Please review our updated Terms and Rules here

Z80 Intel hex loader

The challenge I think you have is that your approach is that it is an end-to-end test of what you've built, which exposes the outcome to any one failure within the system. It may be that you need to test each element much as you did with the latch/read circuit earlier on.

If you use a PC to generate the RS232 signals, you can run a terminal which will show whatever is received and acts as a known constant against which to test the board. Also, if you managed to get a logic probe, it will quickly highlight unanticipated errors related to baud rate and signal framing. Making sure that you're communicating correctly with the chip is also useful. But even a logic probe will tell you when the pulses have left a TX line due to the start bit if nothing else. Using the PC will also tell you quickly whether your problem is with the TX or RX side of things.

Also, reading back a register you've written, or a bit status from the control lines will confirm you're talking to the chip correctly.

It sounds like you're most of the way there - with just a little troubleshooting to finish it.
Well, I have some excellent news, this contraption seems to now work. At least on the outputting of data on one of the channels I tested. I figured, since the hardware design is pretty much the same as the serial console port on the CPU card, and the serial card I put together, are the same, why not just use a slimmed down version of the monitor program that drives the CPU card? So, I stripped out all but the commands to display memory locations, send data out the port, get data from the port, and a CP/M return. And I changed the serial port info in the program to still use the console for operator I/O, but the ports on my card to transfer actual data. I watched LEDs flicker, and saw data captured on the other end. Now after a bit more testing, I can move on to the next project, a printer driver card, and finishing up my printer program... And I want to thank everyone for all their help. I have learned a great deal!
Well, here is the schematic of the board as it stands, and the software for one of the ports. I still haven't performed a complete test, but what I have tested is working fine.


  • Port24Loader.txt
    25.4 KB · Views: 2
  • SerialACardv6.pdf
    85.2 KB · Views: 3