|Re: HP-41 printer interface question. (To the M-code gurus out there)|
Message #2 Posted by Eric Smith on 29 Jan 2012, 4:40 a.m.,
in response to message #1 by Diego Diaz
For the flag tests of the "intelligent peripheral" chips, the peripheral puts the flag value onto the ISA line during bit time 0. The CPU copies that to the carry flag.
This is for any instruction of the form hexadecimal x03, x43, x83, or xc3 (x being 0, 1, 2, or 3), in a sequence following a peripheral select instruction (x24, x64,xa4, xe4). It does not apply to the "normal" x03, x43, x83, xc3 instructions, which are jump instructions.