13 Mar
2003
13 Mar
'03
11:01 a.m.
You didn't put the programs in RAM, it still
require one
to blow 1702's that you'd replace those on the SIM4 board
to test out your programs. You need to remember this
is a Harvard architecture type processor. The motherboard/box. . .
Harvard architecture, yes. But the 4004 had a nifty instruction called WPM
(Write Program Memory.) With this instruction - and the appropriate logic -
you can write into RAM and then use bank switching techniques to execute
from it. I use this method along with the 4289 in my
4004 computer to let me
interactively read, write, and execute from any portion of
the 16K (bytes)
of RAM. The 4040 expanded on this idea and added a RPM (Read Program Memory)
instruction.
Bill Kotaska