From theom+news@chiark.greenend.org.uk Sat Dec 2 12:57:14 2006 Path: ewrotcd!not-for-mail From: Theo Markettos Newsgroups: comp.sys.acorn.hardware Subject: Re: Dead A4, help please. Date: 02 Dec 2006 12:56:20 +0000 (GMT) Organization: University of Cambridge, England Lines: 65 Message-ID: References: <81eeb4874e.Michael@armpowered.co.uk> <5GD*+ynwr@news.chiark.greenend.org.uk> <8b89898a4e.Michael@armpowered.co.uk> <2e99e18e4e.Michael@armpowered.co.uk> NNTP-Posting-Host: chiark.greenend.org.uk Originator: @chiark.greenend.org.uk ([193.201.200.170]) Xref: news.chiark.greenend.org.uk comp.sys.acorn.hardware:49803 Michael Hambley wrote: > In message > Theo Markettos wrote: >> It might be. If you had a stuck FIQ or IRQ, for example, that might be >> what's stopping it booting. > > If this was the case how would I go about unsticking it if it is possible? It'd be a case of finding out what was causing it. To do this I'd look at these pins on the IOC (VL86C410): /IL7 - /IL0 (33-40): Interrupt inputs, level sensitive /IF (41): Interrupt input, falling edge sensitive IR (42): Interrupt input, rising edge sensitive FH1-FH0 (31-30): Fast interrupt input, active high /FL (32): Fast interrupt input, active low /POR (28): Power on reset, Schmitt trigger active low C5-C0 (49-44): General purpose inputs (active low for interrupting) /IRQ (51): Interrupt request to ARM, open drain /FIRQ (50): Fast interrupt request to ARM, open drain If you can spot one of the interrupt inputs active (probably one of the FIQ inputs) then that might be the cause, and you can then work out which device (see OS_ClaimDeviceVector in the PRMs/Stronghelp for more details of what RISC OS uses them for): These are the A5000/A4/A3010/A3020/A4000 definitions: Pin IOC Register RISC OS device number /IL6 IRQ A bit 0 IRQ 0 Printer interrupt /IL7 IRQ A bit 1 IRQ 1 Low battery warning /IF[*] IRQ A bit 2 IRQ 2 Floppy disc index IR IRQ A bit 3 IRQ 3 Vsync pulse POR IRQ A bit 4 IRQ 4 Power on reset Timer 0 IRQ A bit 5 IRQ 5 (no external pin) Timer 1 IRQ A bit 6 IRQ 6 (no external pin) IRQ A bit 7 FIQ downgrade (generated by OS) /IL0 IRQ B bit 0 IRQ 8 Podule FIQ downgrade /IL1 IRQ B bit 1 IRQ 9 Sound system buffer change /IL2 IRQ B bit 2 IRQ 10 Serial port interrupt (also FIQ 4) /IL3 IRQ B bit 3 IRQ 11 IDE interrupt /IL4 IRQ B bit 4 IRQ 12 Floppy interrupt /IL5 IRQ B bit 5 IRQ 13 Podule interupt IRQ B bit 6 IRQ 14 KART keyboard buffer Tx empty IRQ B bit 7 IRQ 15 KART keyboard buffer Rx full FH0 FIQ bit 0 FIQ 0 Floppy DRQ FH1 FIQ bit 1 FIQ 1 FH1 pin on IOC FL FIQ bit 2 FIQ 2 Econet fast interrupt /C3 FIQ bit 3 FIQ 3 C3 pin on IOC /C4 FIQ bit 4 FIQ 4 Serial port fast interrupt (also IRQ 10) /C5 FIQ bit 5 FIQ 5 C5 pin on IOC /IL0 FIQ bit 6 FIQ 6 Podule fast interrupt [*] This is actually marked on the datasheet as -IL, but I think that's a typo > I've been quite busy with some contracting work I've managed to pick up just > now, replies are taking a while to come from me so I thank you for your > patience. That's OK, I'm not in a hurry :) Theo