Is anything else contributing to LS244, though I expect not. It looks like it's read at &FC50 with a BIT operation to transfer bits 7 and 6 to the N and V flags. Is any logic connected to either the IRQ or NMI line on the bus connector?Prime wrote: ↑Mon May 21, 2018 5:25 amINTRQ -> IC6-LS244 pin 17Pernod wrote:Just whether either of IRQ and NMI lines are connected.
DRQ -> IC6-LS244 pin 2
The outputs from those buffers go to Pin 18 to D7, Pin 3 to D6.
This suggests to me that the DRQ and INTRQ are polled by reading an IO register which triggers the gate on the LS244. There is also an LS273 latch on there which I suspect is the drive control latch.
The MTX512 floppy devices do something similar and I never managed to get them working either.