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Re: 65c816 "Core"
Posted: Mon Sep 27, 2021 3:35 am
by GamerFox
This is a bit of a tricky problem: Should I put the IRQ# lines from the RTC and the UART into the control lines of the 65C22s or should I have them go into, say, a 74LVC21 that outputs direct to the IRQ# input of the microprocessor? I already have the SD detect switch go to CA1 on VIA1 but that's a special case because I'm thinking of flipping its CA1 control from positive-edge to negative-edge and vice versa depending on what the switch state is.
Re: 65c816 "Core"
Posted: Mon Sep 27, 2021 10:32 am
by BigEd
If you route the interrupts through the VIA's pins, you get some control of which ones are active or not, and can switch between interrupt-oriented and polling for the various devices. Sounds like a win, if you have the VIA, and enough free inputs.
Re: 65c816 "Core"
Posted: Mon Sep 27, 2021 8:00 pm
by GARTHWILSON
The RTC and UART allow turning off interrupts at the source, right? But the VIA's CA1, CA2, CB1, and CB2 are only edge-triggered for interrupts, not level-sensitive, probably meaning you won't want to put more than one interrupt source on each of these pins. There might be a good reason to run the peripherals' interrupt output lines into IRQ\ instead. Additional hardware can be used to read what the source of the interrupt is, if you don't want to poll each device in software. The software polling is often done taking a lot more cycles than necessary though, checking all interrupt sources even if most of them aren't even enabled at the moment, and not going in the best order ("best order" being that you first poll the devices that are most likely to cause an interrupt, or the ones that would be most urgent to service).
Re: 65c816 "Core"
Posted: Mon Oct 04, 2021 11:51 pm
by GamerFox
Well, I had to change out a few of the discrete logic chips because they were either non-existent or didn't have a through hole version. I'll do some timing calculations and if it works out, I'll post a new thread about what I'm making in the Hardware section I guess?
Re: 65c816 "Core"
Posted: Tue Oct 05, 2021 9:47 am
by BigEd
Sounds great!