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Thread: CBM 8032 Character Display Problem

  1. #21

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    Hi Andy,

    I'm from Luxembourg in the middle of Europe.

    Andreas

  2. #22
    Join Date
    Feb 2009
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    Southern California, USA
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    Quote Originally Posted by Andreas Zock View Post
    I bought four 2532 EPROMs today because they are pin compatible with 2332 ROMs.
    But would a 2716 also work, because the pin layout is a bit different?
    Andreas,
    Good question. In the 8032 PET, as a character generator, the chip selects in the ROM/EPROM should always be enabled (low). So pin 18 is tied to CHR Option in the CRT Controller which will be low in this application and pin 20 is tied to ground. In the 4K byte 2532 pin 18 is not a chip select but address line A11 input. So as long as the information is programmed into the lower 2K of the EPROM, it will work fine as the A11 input will always be low.

    In the 2K byte 2716 both pins 18 and 20 are 'chip enables' so being held low will also work fine.

    EDIT: By a coincidence of pinouts, a 2732 EPROM can be used in this socket if the data is programmed into the upper 2K of the EPROM! See pin 21 (A11) of the 2732.
    Last edited by dave_m; September 14th, 2017 at 11:55 AM. Reason: added 2732 info

  3. #23

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    Today, I replaced the 901447-10 character ROM with an 2732 EPROM, where the data is programmed in the two upper kilobytes starting from 2048.
    I measured 5V on the pin 21, so the address pin 11 will be high.
    And yeah, the CBM 8032 is back alive
    20171011_161157.jpg
    Thank you all for you help.
    With your help we saved another Commodore

  4. #24

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    Today I replaced the faulty character ROM with an 2732 EPROM in which I programmed the data in the upper 2K.
    And yeah it is fully working now
    Many thanks for your help!
    With your help we brought another Commodore PET back to live

    program_901447-1.jpg

    working_character_rom_8032.jpg

  5. #25
    Join Date
    Feb 2009
    Location
    Southern California, USA
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    2,362

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    Good work fixing your Commodore PET!

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