notANON

In trying to understand the PLO (put low bit in D) and the GLO (get low bit from D) commands, I’m going to write a program that cycles through R1-RF and increments the registers one at a time.  This program is pretty darned boring unless you have the memory contents in full view on the emulator.  Let’s get started:

0000      90      GLO         Set D to zero

0001       A1      PLO         Set R1 to zero

0002      11       INC          Increment R1 (This is the start of where we loop it)

0003      91      GLO         Set D to value of R1

0004      A2     PLO         Set R2 to value of D

0005      92     GLO         Set D to value of R2

0006      A3     PLO         Set R3 to value of D

0007      93     GLO         Set D to value of R3

……      and so on and so on until  …….

0020     30      BR            Unconditional branch to the next byte

0021      02                       Start the program again from 0002

I would suggest running this program in step mode.  This program was designed to HAMMER DOWN the function of these two commands for me.  It’s very illustrative of what these commands do if not a bit repetitive.

I’m starting to wonder how I can write a byte to a specific location in memory now.  Specifically right after a 64 OUT 4 command.  It would be nice to get some of the output devices involved in the fun here.  I have some ideas of how it might work but I’m sweating with anticipation.

Another AHA moment!  The BR 30 (Branch Unconditionally) command is simply changing the value of whatever register that P is pointing at.  The value of P can be changed by the Dr SEP (Set P) command.  It’s starting to all make a bit more sense.  (Pun intended)