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Thread: Intel D8741A peripheral MCU

  1. #1

    Default Intel D8741A peripheral MCU

    Hi folks,

    I'm working on restoring a 1984 executive desk phone system made by STC called the Executel 3910, an 8085-based autodialling phone system and viewdata/Prestel terminal rolled into one. One of the controllers in there is a D8741A with 1K EPROM space which I can read so thankfully that part of the chip is OK, and I'm guessing it's used as a keyboard controller but does anyone know of a disassembler?

    I have a reference book for the Intel MCS85 development system which contains good writeups for both this controller and the 8085A which has helped the restoration procedure, but seeing the code would help a lot too, particularly in the 8085A initialisation where it appears to loop for a while waiting for something to happen.

    Cheers

    Witchy
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  2. #2

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    Hm, actually I might've sussed it. Pete Clare's dASMx claims to dissassemble the MCS85 family of chips and it LOOKS like it's produced readable code. I just need to look up the instruction set now

    W
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  3. #3

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    Quote Originally Posted by Witchy View Post
    Hm, actually I might've sussed it. Pete Clare's dASMx claims to dissassemble the MCS85 family of chips and it LOOKS like it's produced readable code. I just need to look up the instruction set now

    W
    The 8741 is 8048 family. The 85 is mostly 8080 with a few extensions.
    They are not compatible at all.
    The 8048 is a harvard architecture. The difference between a 8041
    and 8048 is the I/O port. The 41 had a 8 bit port with handshake.
    Anything for the 8085 would be useless.
    Dwight

  4. #4
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    Default

    Post the 8741 binary code as an attachment here. I would be curious to take a quick look. I just happened to write a simple 8041 disassembler of my own yesterday for a project. (Looking at the 8741 keyboard/display controller of the iUP-201).

  5. #5
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    Default

    Sprechen Sie Linux? There's an 8048/8041 disassembler for that platform here

  6. #6

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    Usually disassembly is an iterative process. Tables and unused
    space takes a little time to identify.
    I write my own disassemblers my self. I may have something for the 41
    because I did disassemble a 8043 code once in a keyboard.
    It was a long time back so would take some digging.
    I needed to modify the key board table since I needed a control @ that
    wasn't supported. I believe the keyboard was from a Franklin.
    Luckily the code was in an outside ROM. I'm not set up to read
    the code in a 8043. Finding the translation table didn't require
    too much understanding of the code.
    Dwight

  7. Default

    There's a DOS-hosted 8041 disassembler which can be found as DISASMV2.ZIP in various places.

  8. #8

    Default

    Quote Originally Posted by Dwight Elvey View Post
    The 8741 is 8048 family. The 85 is mostly 8080 with a few extensions.
    They are not compatible at all.
    The 8048 is a harvard architecture. The difference between a 8041
    and 8048 is the I/O port. The 41 had a 8 bit port with handshake.
    Anything for the 8085 would be useless.
    Dwight
    Indeed, I found that out shortly after posting my 'never mind' reply, lots of manual reading while customer things happened at work and when I got home I discovered the d52 disassemblers Chuck mentions. The dz80 utility (part of the d52 suite) does a pretty good job of separating out the text portions of the code and verifies what I thought in that the init routine I've been looking at is basically 3 distinct delay loops.

    W
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  9. #9

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    Quote Originally Posted by gslick View Post
    Post the 8741 binary code as an attachment here. I would be curious to take a quick look. I just happened to write a simple 8041 disassembler of my own yesterday for a project. (Looking at the 8741 keyboard/display controller of the iUP-201).
    Here you go:
    D8741A.zip
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  10. #10
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    Quote Originally Posted by Witchy View Post
    Here you go:
    D8741A.zip
    You have probably found and run some 8041A disassembly tools by now. Attached is how I disassembled it myself with the code that is obviously reachable through either the reset vector or the timer interrupt vector. The bytes at the IBF vector does not appear to be valid code. I didn't spend any time looking at the code to try to guess what any of it might be doing.
    Attached Files Attached Files

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