HP-41C HP-IL REMOTE & LOCAL commands

[J-F Garnier]

(06-06-2018 01:04 PM)rprosperi Wrote:  As Sylvain suggests, a frame-by-frame breakdown of each high-level command is the best way to understand and use them, and I always thought such documentation should have been provided by HP, even if only in a separately purchased "advanced" manual or something similar.

On the 41, the HP-IL is deliberately automated as much as possible, contrary to the 71 where you have a more precise control of the HP-IL.
First the loop addresses are re-assigned in almost all HP-IL commands so you can add/remove devices at any time, and everything will still work - on the 71 you have to do a RESTORE IO to re-assign the addresses.
Then, the HP41 checks for a printer almost every time it does something, to check for instance the trace mode on the 82162.
And, worst, if a printer is on the loop and in AUTOIO, the HP41 continuously emits IDY frames to check if the user pressed a key on the 82162 (even if that printer is not actually present).

So if you want to look at the low-level frames related to a high-level HP-IL command, I recommend to put the printer switch of the 82160 module in the disable position.

J-F