Tony Firshman wrote:
When we were configuring the parallel port, we had to disable IRQ (7 I think)
A completely different issue. The parallel port IRQ is edge-triggered, if the port is in SPP mode. I originally planned to use not the SPP but the EPP/ECP mode where it was possible to generate level triggered IRQ's on the I/O cards I had used. All other IRQ's (including Ethernet, serial, IDE, Floppy) are level-triggered, so I saved the Flipflops to support edge-triggered IRQ.
Trouble was that TT had problems with the EPP/ECP mode, when using other cards than the one I originally supplied. To support a broader range of cards he had to use SPP mode, so the parallel port IRQ (and *only* that one) had to be disabled.
and TT had to do it in software (by timing carefully - ie slowly!).
I think TT made things too complicated when he wrote that driver. To prove him wrong, I wrote a PAR driver for QDOS with a different approach, which works at full speed (at least for the printers I tried).
The hardware needs a permanent change in state but the ISA hardware provides a pulse, which is not seen by the Q40 hardware. I think the Q60 is the same. Peter said at the time there was no spare logic left.
Yep.
Peter needs to be consulted here I think - as my knowledge now is probably way out of date, and Peter may have found a way of 'seeing' the IRQ pulse.
Your knowledge isn't out of date, but it only applies to PAR in SPP mode :-)
All the best Peter
