Printing Polling Question

[reifsnyderb]

I am trying to figure out how the Atari computer knows the printer is ready for more data.  Looking at the Altirra Performance Analyzer, it's clear that the computer first does a status request.  The printer then responds with an acknowledgement, and the computer follows up with numerous 40 byte data frames. 

 

On a real hardware, with a 1025 printer, the computer can be tied up for ten minutes (or more) to print out a document.  So, my question is what is the polling process the computer uses to find out if the printer is ready for more data?  I've looked through both the OS source code, the Altirra Hardware Manual, and the Atari 400/800 Technical Reference Notes.  Admittedly, I could have missed something.  My thought is that maybe the computer requests the status from the printer until it the printer responds?  I didn't see any capability for the printer to reply to state it's ready for more data.

 

Looking through the OS printer handler and SIO sections, it almost appears that this sort of thing is handled by the application?

 

Thanks!

[phaeron]

Think it's simpler than that and the printer just holds Complete until it finishes printing a line -- at least that's what my partial 1025 firmware disassembly implies.

 

[reifsnyderb]

24 minutes ago, phaeron said:

Think it's simpler than that and the printer just holds Complete until it finishes printing a line -- at least that's what my partial 1025 firmware disassembly implies.

 

Just to confirm I understand:  When the printer is printing, it provides a bus response of $43 (or C/complete).  When the printer is ready for data, it provides a bus response of $41 (or A/ Acknowledge)

 

Thanks!

Edited October 5, 2023 by reifsnyderb

[phaeron]

Standard SIO protocol: computer sends write command, device sends ACK, computer sends data frame, device sends ACK, device buffers data and/or prints, device sends Complete.