Anyone with experience with the 87c75x series

Discussion in 'Embedded Systems and Microcontrollers' started by Aule Mar, Jul 28, 2010.

  1. Aule Mar

    Thread Starter New Member

    Jul 27, 2010
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    I picked us a dozen of these really cheap and figured I would make a programmer for them. This family of chips uses a 10-bit serial command (at 2Mhz) to select the different program modes of the chip (read, verify, encrypt, security, and signature (chip type).. I searched the internet and couldn’t find any programmers out there. So I designed one myself based on the 87c751 data sheet information.
    It turned out to be fairly complicated but I completed the programmer, which is driven by the parallel port of a PC. It provides the required input signals as specified by the data sheet. But I don’t believe the serial command sequence is working. Before trying to burn code into one I figured I would just try to read the signature byte. An operation that is relatively simple. Just send a 294h serial command to the reset line, present a 1Eh to the address line, and read the data which should be 9Fh for the 87c751.
    Does anyone have experience with the 87c75x series processors? I have a few questions... Has anyone seen a programmer design for them? Could you point to it or post it here. If someone would like to see it, I’ll post my design here, I used ExpressSCH, converted to PDF's.
    Thanks
    Aule
     
  2. Aule Mar

    Thread Starter New Member

    Jul 27, 2010
    4
    0
    I see a number of folks have looked at this but no responces so far. Figure I'll post the schematics of the programer, and see what folks think. There are three schematics that all tie together, First is the main control logic for reading & writing addresses and data, second is the pulser that provides the required 25 programming pulses, and third the mode control serializer to set the 87C751 into its different modes..
    The mode control logic raises the Reset line (also control input for the 87c751) hi for 24 clock cycles (2 machine cycles) just prior to shifting the control data out (29xH); LSB first, synced, to the X1 clock, and stable during clock hi; and then dropping the line low and then keeping it low.

    Aule
     
    Last edited: Jul 29, 2010
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