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Thread: REMEX Paper Tape reader

  1. #31

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    'BUILD' uses the header block when it's incorporating a handler into the system build. The USR routines are used by the calling program to load and use the handler and provide the entry point(s). It's not loaded at *200, but BUILD expects it to be assembled there, it can be loaded at (more or less) any page in field 0 at an address specified by the calling program. The format's reasonably well specified in the BUILD writeup and the USR routines are glossed over, but enough to use.
    Last edited by bobaboba; October 15th, 2018 at 09:10 AM.

  2. #32
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    So, I need to read about the USR's? Thanks Mike

  3. #33

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    Well, probably only for completeness if you're going to be using only system programs since that'll deal with them transparently, you'll only be worried about USRs if you're going to write something new. Since you've got the source for the PTP/PTR one to hand now it's a pretty straightforward job to hack it to suit a different peripheral. You're not writing a system handler which has more constraints, so you just need to strip out the (say) PTP/PTR-specific routines and pop in your own, leaving the bits which deal with the data and buffer handling. If (as I assume) you're creating only a different PTR handler here there should be tons of room as you'll can strip out all of the punch stuff. You need to decide what to call the device (or if you don't have another one just leave it as PTR. The header will need minor mods to change the number of devices from 2 to 1. After that just run BUILD to incorporate and test the new handler.

  4. #34
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    That's what I was thinking. I like to understand at least some of how things work. I don't plan changing the name PTR will work just fine. My handler will not have PTP, so there will only be one device in the handler. I think all I have to do is replace the RXX commands with subroutines for the REMEX. Then try it, then fix it until it works. Thanks Mike

  5. #35
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    I've been working on understanding the PT8E device handler code. There are some items in the code that I am unfamiliar with and there are some new methods that I have learned. Anyway I have a question. If in a delay loop a constant is added in the loop how much time does the PDP8 use when passing through the constant. Here is an example

    Code:
    START, CLA
               TAD N1
               ISZ N1
               JMP .-1
               HLT
    N1,       0
    This loop should use up about 4096*3.8uSec=15.6 mSec. Then if a constant is added to the inside of the loop, how much longer is the time loop?

    Code:
    START, CLA
               TAD N1
               ISZ N1
               XYZ=RST
               JMP .-1
               HLT
    N1,       0
    This loop would take 4096*(3.8uSec+x). x would be 0, 1.2uSec or 2.6uSec.

    Thanks Mike
    Last edited by Mike_Z; Yesterday at 02:13 PM.

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