Lost on a Z80 SBC

Discussion in 'Embedded Systems and Microcontrollers' started by 1337sh33p, Aug 10, 2010.

  1. 1337sh33p

    Thread Starter New Member

    Aug 9, 2010
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    Hey -

    I've been interested in the z80 for quite a while ( even wrote an emulator), and I saw a pretty cool looking z80 sbc on eBay, so I bought it.

    However, it arrived, and though I can find a lot of info about the individual chips (through datasheets etc), I can't find any info on the board online ( it says Infinity group inc. Rev 6 on it, but there doesn't seem to be a model #) and I find myself at a loss for where to start. The only included documentation was a single sheet basically listing te chips on the board.

    I just want to be able to experiment with z80 programming on it, and possibly use it in a later project.

    Can anyone offer any advice, hints or other information?

    I can take pics of the board/ docs that came with if needed .
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Is there a socketed EPROM on the board? You may have to pull it to program it externally. Sounds like accessing external devices could be a challenge if you do not have I/O addresses.
     
  3. 1337sh33p

    Thread Starter New Member

    Aug 9, 2010
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    Thanks for the help. Sorry if I seem to be jumping around, but I'm actually starting to understand a lot of these things as I type them out.

    I now know that there are 3 8255's for IO (D8255AC-2's), and I understand most of the pin trace for them.

    The Two Issues that I am having are

    Firstly , near the bottom of the pin trace there is listed the following:

    (the edge connectors are labeled e1-e72. )

    I included pin 40 to contrast with the top 24 pins which make some sort of sense, but I really am having trouble understanding the CL-001. It is a big SMD chip (the only one, all the rest are DIP) with 144 pins, but no distinguishable model number. A0 and A1 are listed on the datasheet as "port address inputs," and CS is "Chip Select Input," but I can't find anything labeled PL5 either.

    Secondly, the addresses for the I/O are listed as
    The datasheet says the pins are programmed in groups of four, so it makes sense that there should be four distinct adresses for each chip, but I have no idea how this works from a software perspective (ie how to switch between Port A, PortB etc, and how to switch between low bits and high bits on each port)

    Finally, does anyone know of any way that the included EPROM (27128) could be replaced with an EEPROM? (I don't have much idea when it comes to UV erasing, and I hope to be messing around with this, ie changing the code a lot)

    I'm sorry if I'm being unclear, or if my questions are obscure / board specific. Thanks for all of the help on this.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The pins from the 8255's are less interesting than the addresses they reside at. The Z80 can't use them unless it can send and receive data and control signals to them. Here is a link to a tutorial - http://www.decisioncards.com/io/tutorials/8255_tut.html

    The address select pins A0 & A1 must be use to select bank registers, as two bits can select 0 - 3. That may resolve part of you problem with

    As to the EEPROM, something like a 28C16 might do - http://doc.chipfind.ru/stmicroelectronics/28c16.htm
     
  5. 1337sh33p

    Thread Starter New Member

    Aug 9, 2010
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    0
    Thanks so much for all the help, I think I pretty much see what I need to do. The only thing is the EPROM, as I would really prefer not to have to go out and buy a UV eraser.

    The chip you posted only has A0 - A10, while the 27128 has A0-A13 (which makes sense considering this allows 16383 combinations, and it has 16kB = 128kb ).

    There are several 32kB EEPROMs with almost identical pinouts, except Vpp is replaced by A14... would I be able to use one of those? this is one of them, and here's datasheet for the 27128

    Thanks again for all the help.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    It seems to be a pain to find parallel EEPROM's. That one I turned up is 2K X 8 (oops). The 32K device should work if A14 is tied low.

    Good luck finding those external device addresses.
     
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