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Thread: Tektronix 4051 Tape Emulator

  1. #11

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    I have not had any success with generating an EOF. Tried all the above suggestions.

    I am starting to think that ON EOF is only handled for the internal tape drive.

    I started looking at the 4051 ROM listings and found the variable PNDEOF used in the REAHDR routine in the BINCTL section.

    But looking through other listings, I can not find where it is set to anything other the 0x80 (internal mag tape EOF)

    Maybe someone more familiar with the listings can verify?

    By the way, does someone have a post linked version of the ROM listing. Or at least a memory map of where the different ROM sections lie?

    Thanks.

  2. #12
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    Try using the TYP(n) function instead. That is what I have seen used in an example program to find the end of file marker. I tried to find the example program last night - but failed. I will have another look again today.

    Dave

  3. #13

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    Quote Originally Posted by oldmicros View Post
    I have not had any success with generating an EOF. Tried all the above suggestions.

    I am starting to think that ON EOF is only handled for the internal tape drive.

    I started looking at the 4051 ROM listings and found the variable PNDEOF used in the REAHDR routine in the BINCTL section.

    But looking through other listings, I can not find where it is set to anything other the 0x80 (internal mag tape EOF)

    Maybe someone more familiar with the listings can verify?

    By the way, does someone have a post linked version of the ROM listing. Or at least a memory map of where the different ROM sections lie?

    Thanks.
    oldmicros,

    Here is an example program using TYP function to see what type of variable is next - or detect EOF

    4050_TYP_example.jpg

    I now think the BASIC EOF function only works with the internal tape and the value in parenthesis must therefore be zero (as the 4050 considers itself to be GPIB device 0).

    I believe the 4924 creates an EOF TYP in a binary file when the 4050 closes that file.

    Monty

  4. #14

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    Quote Originally Posted by oldmicros View Post
    I've read with interest the recent 4051 discussions here and have noticed that a tape emulator has been mentioned. I too have recently repaired a 4051 and since the tape drive is not functional, I am looking for alternatives. I thought it would be nice to just throw a bunch of images on an SD card and access via the GPIB. I was working on a similar project for the HP series 80 machines so already have a microcontroller wired to an SD card and HPIB drivers. I was planning to work on this over the holiday break when I have some spare time. Is anyone else actively pursuing this? Does this sound useful or is there a better way? I'd prefer not to have to connect to another computer to load programs.
    Thanks,
    Bill
    When you say it's not functional do you mean it doesn't do anything at all, or doesn't read/write successfullly?

  5. #15

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    By not functional I mean unable to read/write. Motor movement seems OK in both directions.

  6. #16

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    Quote Originally Posted by oldmicros View Post
    By not functional I mean unable to read/write. Motor movement seems OK in both directions.
    How is the tension on the tape you are testing with? If the tension is too low - you can't read the tape.

    If you pull open the spring loaded cover where the tape head contacts the tape and push in on the tape gently with your thumbnail (so you don't get finger oil on the tape) - the tape should deflect about halfway to the inside edge of the cartridge. If it deflects more than that - it is too loose.

    Old cartridge drive belts are a typical problem - they loose tension or they are broken.

    I've had success replacing the old drive belts with a belt from a DC6250 tape (they are much newer than the DC300/DC600 tapes).

    Monty

  7. #17

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    Quote Originally Posted by oldmicros View Post
    I have not had any success with generating an EOF. Tried all the above suggestions.

    I am starting to think that ON EOF is only handled for the internal tape drive.

    I started looking at the 4051 ROM listings and found the variable PNDEOF used in the REAHDR routine in the BINCTL section.

    But looking through other listings, I can not find where it is set to anything other the 0x80 (internal mag tape EOF)

    Maybe someone more familiar with the listings can verify?

    By the way, does someone have a post linked version of the ROM listing. Or at least a memory map of where the different ROM sections lie?

    Thanks.
    Actually I do have a memory map of the 4051 ROM entry points posted in the 4051 Assembler documentation on my Tektronix 405x program repository:

    https://github.com/mmcgraw74/Tektronix-4051-4052-4054-Program-Files4051-Assembler/Tek 4051 Assembler Program Instructions Tekniques Vol 7 No4 062-7456-01.pdf
    Last edited by nikola-wan; July 22nd, 2019 at 03:41 PM.

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