TI 58/59 ROM modules and OP instructions

[Dieter]

(01-01-2018 05:25 PM)Maximilian Hohmann Wrote:  I do not know if and why it was generally avoided to use OP commands in solid state software modules, but there are exceptions: The Aviation Module for example has routines (like "AV-04 Long Range Flight Plan") that will produce labelled printouts on an attached printer. This is only possible using OP instructions.

Now that you mention it: the standard module's ML-01 program includes some printed text output as well. There is a test routine that, after it has been successfully completed, prints "MASTER" and "1.". And indeed subroutine WRT contains OP 00 (clear print buffer), OP 03 (set buffer #3) and OP 05 (print buffer).

Also the Math/Utilities ROM has a program (MU-20) that returns various status information, including the memory partition. This requires OP 16, so this might be another example.

So OP commands were possible in TI's ROM modules. This leads to the question why they were (mostly) not used despite their obvious benefits.

Dieter