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Chuck(G)

  1. Cloning a PAL/HAL - Part 8

    Part 1 of this series.

    A very common part is the PAL16L8, a 20-pin device (Datasheet). You'll see this part on vintage gear a lot after about 1988.

    Like the PAL10L8, there are 10 inputs, but there's a twist. Where the PAL10L8 had 8 dedicated outputs, the PAL16L8 allows 6 of these signals to be programmed as inputs or outputs. Thus, we can have 10 inputs and 8 outputs, 11 inputs and 7 outputs,...16 inputs and 2 outputs. You can see that the PAL16L8 can replace a ...

    Updated October 25th, 2011 at 04:21 PM by Chuck(G)

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  2. Cloning a PAL/HAL (Part 7)

    To see Part 6, click here

    To go to Part 1, click here


    Finally, you program the GAL with your programmer. For this one, I used an inexpensive programmer, the Chinese TOP853. These are sold on eBay, and if you're patient, you can pick one up for about $25, shipped. Mine worked right out of the box.

    It's a good idea to erase the GAL before programming, even if it's brand-new. A random sampling shows quite a few with some fuses blown.

    ...

    Updated October 25th, 2011 at 04:23 PM by Chuck(G)

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  3. Cloning a PAL/HAL (Part 6)

    Part 5 of this series can be found here.

    In the previous post, we discussed using Minilog to derive our GAL equations from PAL raw data.

    We fed Minilog the following data:

    Code:
    table PAL10L8
      INPUT I9 I8 I7 I6 I5 I4 I3 I2 I1 I0 
        OUTPUT O7 O6 O5 O4 O3 O2 O1 O0 
      0000000000 00001011
      0000000001 00001011
      0000000010 00000010
      0000000011 00000010
      0000000100 00000011
      0000000101 00000011
    ...

    Updated October 3rd, 2011 at 07:48 PM by Chuck(G)

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  4. Cloning a PAL/HAL (Part 5)

    Part 4 of this series can be found here.

    Rather than pulling hair and drinking lots of coffee trying to manually figure out how PAL inputs are related to PAL outputs, we can investigate some reduction methods.

    If you took computer engineering in school, you probably remember the Quine-McCluskey algorithm. There's plenty of material on the web about it, but it's not particularly efficient, particularly as the number of terms increases. There is also Petrick's Method, ...

    Updated October 3rd, 2011 at 07:46 PM by Chuck(G)

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  5. Cloning a PAL/HAL (Part 4)

    You can find Part 3 of this series here.

    Recap thus far: We have a PAL10L8 that we need to duplicate. We've constructed a simple circuit, that driven by a PC parallel port and a bit of software will iterate through all 1,024 input possibilities and record the output.

    We need to get a series of logic equations, one for each output pin that will produce the same results from the input pins as our original PAL.

    We can do this the easy way or the hard way. The ...

    Updated October 4th, 2011 at 02:26 PM by Chuck(G)

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