Tektronix 4051 magic mode found!

From: Joe <rigdonj_at_intellistar.net>
Date: Tue Feb 23 18:52:12 1999

Rick,

  Thanks, that's a big help. I wouldn't have ever figured that out by myself.

   Joe

At 12:59 PM 2/23/99 -0800, you wrote:
>>
>> Try "Exec". I don't have any details of how to use it, sorry. Let me know
>> what you find out.
>>
>
>Hmmm...this brings back some memories. From my recollection, this
>statement accepted a string argument. The character string supplied
>was coded in a special pseudo-hexadecimal:
>
>0="0", 1="1", 2="2", 3="3", 4="4", 5="5", 6="6", 7="7"
>8="8", 9="9", a=":", b=";" c="<", d="=", e=">", f="?"
>
>For example, to represent the hex sequence 6e7f391d, the string would be
>"6>7?391="
>
>Each two characters represent a byte.
>
>Now, using this method, you could 'code' 6800 machine code instructions.
>
>The EXEC statement would store the bytes supplied in the string argument
>as a linear sequence of machine code, and cause a jump to the segment
>of code. I don't recall if it was JMP'd to, or JSR'd to...and don't
>remember any of the details of how to return from a segment of code
>executed with the EXEC statement. Obviously, sending random stuff
>to an EXEC statement could wedge the machine up.
>
>I remember that EXEC was used frequently by folks who were experts
>with the machine (and had magic lists of the internal runtime
>calls) to make game programs and stuff in machine code that would
>run much faster than the interpreted BASIC. It also allowed
>'extensions' to BASIC that you could use to do things like PEEK and POKE,
>etc. There were conventions for passing variables in and out of
>EXEC'd code, so BASIC could be used for 'high level' functions, and
>the fast EXEC'd machine code could be used for time-critical or
>other functions that were too slow, or too tedious (IE: bit manipulation)
>to do in BASIC.
>
>Hope this helps. It's all from foggy memories..all the fun with 4051's
>that I had happened sometime around 1978...21 years ago. I'm amazed
>that I can remember ANY of it, given that many times I can't remember
>where I put my car keys :-)
>
>Rick Bensene
>
Received on Tue Feb 23 1999 - 18:52:12 GMT