Looking for info on the internal workings of the 41's IR printer module

[J-F Garnier]

(05-09-2016 08:00 AM)Mike (Stgt) Wrote:  Is there an HP41-Emulator that runs Blinky's firmware in some useful way?

I once tried to trace the code to understand how it works.
Below are my notes ... not sure it's useful for you...

J-F

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IR ROM uses:
DATA registers 20 to 2D seems implemented with only one byte.
They are used in the TESTP function, are they elsewhere??
Seem to be the same registers than the peripheral ones.

smart perf 9 (same than 82143 printer, but with different opcodes):
14 registers 0 to D (same than the one accessed through DATA20-2D?)
opcodes are:
RDPTRN n
CH= cmd

to write C[1-0] into register n (0<n<D), the sequence is used:
SELPF 9
CH =nE

to read register n (0<n<D) into C[1-0]:
SELPF 9
RDPTRN n
CH= 01

Combined sequence:
6833 264 SELPF 9
6834 138 CH= 4E (78)
6835 1FA RDPTRN 7
6836 005 CH= 01 (1)
This writes C into reg4 and read reg7 into C