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How to restore the bootloader of a AT89C51RD2?

Eduardo L Marcovecchio

Hello everyone,

I got some AT89C51RD2 chips that had their original bootloaders overwritten. Now I can't use FLIP to reprogram them.

AFAIK, now I need a parallel programmer to erase the chips and reflash the original bootloader.

So, I have two questions:

1) Where can I get the bootloader hex file for this specific chip?

2) Which parallel programmer should I use? I can build it if I can get the schematics.

Thank you all in advance!

Eduardo

Parents
  • 0 in reply to ²erik malund

    Good idea, Erik! If nothing else works, I'll certainly do that.

    However, following your last post, I went after some older datasheets, the ones that still bring information on parallel programming, and see this info I found on AT89C51RC, quite interesting:

    "Chip Erase Sequence: Before the AT89C51RC can be reprogrammed, a Chip Erase operation
    needs to be performed. To erase the contents of the AT89C51RC, follow this sequence:
    1. Raise VCC to 6.5V.
    2. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
    3. Power VCC down and up to 6.5V.
    4. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
    5. Power VCC down and up."

    This is quite easy to implement. And it may work, according to the AT89C51RD2 datasheet:

    "Only a full chip erase in parallel mode (using a programmer) or ISP command can reset the soft-
    ware security bits."

    So, it seems all I need to do is to build a simple circuit to feed 6.5V to Vcc thru a transistor, and write some simple code for a working MCU to signal the transistor and ALE at the correct timings.

    Since this won't take a long time to implement, I'll give it a shot. What do you think about this possible solution?

    Thanks for the help!

    Eduardo

Reply
  • 0 in reply to ²erik malund

    Good idea, Erik! If nothing else works, I'll certainly do that.

    However, following your last post, I went after some older datasheets, the ones that still bring information on parallel programming, and see this info I found on AT89C51RC, quite interesting:

    "Chip Erase Sequence: Before the AT89C51RC can be reprogrammed, a Chip Erase operation
    needs to be performed. To erase the contents of the AT89C51RC, follow this sequence:
    1. Raise VCC to 6.5V.
    2. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
    3. Power VCC down and up to 6.5V.
    4. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
    5. Power VCC down and up."

    This is quite easy to implement. And it may work, according to the AT89C51RD2 datasheet:

    "Only a full chip erase in parallel mode (using a programmer) or ISP command can reset the soft-
    ware security bits."

    So, it seems all I need to do is to build a simple circuit to feed 6.5V to Vcc thru a transistor, and write some simple code for a working MCU to signal the transistor and ALE at the correct timings.

    Since this won't take a long time to implement, I'll give it a shot. What do you think about this possible solution?

    Thanks for the help!

    Eduardo

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