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Thread: Bytesaver ii questions.

  1. #1

    Default Bytesaver ii questions.

    I'm going to attempt to try a Bytesaver II in my Sol-20 and program some 2708's. I have three questions:

    I have attached the recommended assembly code from the manual, it is for a Z-80 CPU. I'm not familiar with all the differences with the 8080, which I am more familiar with.

    1) What would be the recommended changes to this code to make it work with the 8080 cpu ?

    2) Also, I have spotted something I'm sure will give trouble in the SOL. In this machine they hijack the the PRDY line (as I recall) with a driver that drives the line high and low, not an "OR". This conflicts with S-100 cards that use this line, for example Matrox video cards being one example. So in that case I had to reconfigure that card to use XRDY instead, which has the same inhitory affect on the CPU and is a free line in the SOL. I might have to do the same for the Bytesaver card since it uses PRDY in the programming process. If I did that hardware modification, what would have to be changed in the code to make that work, if anything ? Probably nothing, but just checking.

    3) Will the 2708L IC's work just as well as the 2708 ? I can get these much cheaper for some reason than the 2708.
    Attached Images Attached Images

  2. #2

    Default

    Hi Hugo
    It looks like the binary would run on a 8080. I don't think I see anything that is specific to Z80.
    Dwight

    Ops I see LDIR
    That isn't in a 8080. You'll need to code that. It reads data from at HL, writes to at DE, and counts BC till 0.
    loop
    MOV A,M
    DCX HL
    XCHG
    MOV M,A
    DCX HL
    XCHG
    DCR C
    JNZ loop
    DCR B
    JNZ loop

    A little messy but should work.
    Dwight

    It takes me a while. I've not done 8080 for some time.
    Dwight

    Oops I see CPD
    Dwight
    Last edited by Dwight Elvey; November 21st, 2020 at 04:17 PM.

  3. #3

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    Quote Originally Posted by Dwight Elvey View Post

    It takes me a while. I've not done 8080 for some time.
    Dwight
    Thanks Dwight, That would have taken me a 100 times longer, or more.

  4. #4

    Default

    I missed CPD. It is another of the memory to memory.loop
    loop2
    MOV A,M
    DCX HL
    XCHG
    CMP M
    JNZ Error
    DCX HL
    XCHG
    DCR C
    JNZ loop
    DCR B
    JNZ loop2
    JMP exit
    Dwight

    Note spotted an error in the first code and corrected.
    Dwight
    Last edited by Dwight Elvey; November 21st, 2020 at 04:26 PM.

  5. #5

    Default

    Also LD A,0FFH should be MVI A,0FFH I guess and LD A,H should be MOV A,H and OR should be ORA.

    I'll have to go over it very carefully. There is also JR that I can't see in my 8080 book, it looks like a simple jump.

    What is the best thing to do with CPD ?...it looks like CPI, followed by a decrement of HL and then BC.
    Last edited by Hugo Holden; November 21st, 2020 at 04:29 PM.

  6. #6

    Default

    Hi
    It is a CMP M, not CPI. see may last updated #4 post. For the reset, you can disassemble the binary.
    All register moves are MOV. The 8080 for loading register pairs is LXI rp, ####.

    Dwight

  7. #7

    Default

    Quote Originally Posted by Dwight Elvey View Post


    For the reset, you can disassemble the binary.

    Dwight
    Thanks Dwight, all makes sense, but I don't understand what "reset" you are referring to.
    Is it exiting the program, if so I can easily exit to a Solos warm boot.

  8. #8

    Default

    Hugo,

    Martin Eberhard wrote a full featured CP/M program that supports all three ByteSaver programmers. I’ve used it a lot with my ByteSaver II.

    https://deramp.com/downloads/eprom_p...ard/bytesaver/

    Mike

  9. #9

    Default

    Quote Originally Posted by Hugo Holden View Post
    2)Also, I have spotted something I'm sure will give trouble in the SOL. In this machine they hijack the the PRDY line (as I recall) with a driver that drives the line high and low, not an "OR". This conflicts with S-100 cards that use this line, for example Matrox video cards being one example.
    In general, boards driving PRDY or XRDY should do so with an open collector buffer or tri-state buffer that is enabled only when the board is addressed The ByteSaver falls into the latter category.

    It looks like the Sol-20 itself only drives PRDY for its own memory access (C000-CFFF) and for its own IN/OUT ports.

    Mike
    Last edited by deramp5113; November 21st, 2020 at 06:12 PM.

  10. #10

    Default

    Quote Originally Posted by deramp5113 View Post
    Hugo,

    Martin Eberhard wrote a full featured CP/M program that supports all three ByteSaver programmers. Iíve used it a lot with my ByteSaver II.

    https://deramp.com/downloads/eprom_p...ard/bytesaver/

    Mike
    Wow ! That is excellent, I can't wait to try it.

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