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  • Bad EPROMs?

    Anyone had experience of a while batch of chips being bad?
    I’ve written a chipset and the car wouldn’t start, swapping the boost chip back (same SW) fixes it, I’ve tried 4 different 87-257 EPROMs from the same batch, 2 brand new and two been through the eraser, and none of them work.
    The chips came as a batch from China (yes cheap) Marked ST but maybe fake?
    Anyone had a bad batch?
    Can you recommend a good source?

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  • #2
    I had a problem when chips went through the burner but the voltage was too low. They appeared to have burnt correctly when checked but wouldn't work. Worth checking your programmer settings and voltages. I have a some spares if you are short.
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    • #3
      Thanks Steve
      I’ve ordered a couple of AMD 87C257s from a UK source so I will try one of those.
      The 27C512 fuel chip I burnt at the same time works no problem so I think the settings must be ok. Unless the 87 needs different settings?? I’ve not had a problem before this batch, except the occasional chip that needed erasing..

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      • #4
        I had similar problem with proms from china they all locks brand new but most of them fail wen programing. I use Labtool48

        Edit: 87C257 nedan diffrent settings

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        • #5
          I use GQ-4X recommended by Dmitri.

          The programmer was set for the correct EPROM

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          • #6
            I found that for the chips to burn properly or at all, the burner needs to be plugged into the wall and not just the USB.

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            • #7
              Originally posted by Morris400 View Post
              I found that for the chips to burn properly or at all, the burner needs to be plugged into the wall and not just the USB.
              Interesting, my burner does have this option.
              I will get a 9v psu and try that.

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              • #8
                I received the 87c257s from the UK seller today and burnt a new boost chip, the car fired straight up. I’ll try burning some of the other chips when I get a 9V supply for the burner, but I suspect the whole batch is duff.

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                • #9
                  Good to hear it's sorted
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                  • #10
                    200ns is too slow for the 12mhz processor in M2.3.2. You need faster ones.
                    That's why it doesn't work. 150ns or 120ns will be fine.
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                    • #11
                      Originally posted by prj View Post
                      200ns is too slow for the 12mhz processor in M2.3.2. You need faster ones.
                      That's why it doesn't work. 150ns or 120ns will be fine.
                      This one worked fine, how can I tell the difference?



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                      • #12
                        Data sheet says 150ns
                        Both are the 87C257-20FI,





                        Last edited by newsh; 25 January 2021, 01:25.

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                        • #13
                          This is not the datasheet you are looking at, it's some BS marketing info.

                          Here is an extract from the actual datasheet:


                          The numbers after signify the guaranteed access time.
                          Some -20 chips are actually able to work a bit faster, but you should never use 200ns chips. Because if they work according to spec (200ns), then it won't run.
                          I am going to spare you the calculation, but the absolute maximum it can to be is 166ns. Higher than that and it won't present the data in time.
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                          • #14
                            Originally posted by prj View Post
                            This is not the datasheet you are looking at, it's some BS marketing info.

                            Here is an extract from the actual datasheet:


                            The numbers after signify the guaranteed access time.
                            Some -20 chips are actually able to work a bit faster, but you should never use 200ns chips. Because if they work according to spec (200ns), then it won't run.
                            I am going to spare you the calculation, but the absolute maximum it can to be is 166ns. Higher than that and it won't present the data in time.
                            That’s great info Dmitri thank you!

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