RE: Unexpected IRQ behaviour on a VIC-20

From: Baltissen, GJPAA (Ruud) <>
Date: Sat, 29 Jul 2017 07:37:22 +0000
Message-ID: <>
Hallo Spiro,

> IRQroutine:  
> 	pla
> 	pla
> 	pla

I start my program from a cartridge ROM so the original IRQ routine is still effective. And that routine pushes A, X and Y on the stack before doing a "jmp ($0314)". I don't need them so I discarded them. The NMI doesn't push anything at all to stack before doing a "jmp ($0316)". 

> NMIroutine:  
> 	lda	#$33
> 	sta	IrqNmiCheck
> 	sei				; disable interrupts
> Why do you want to disable the interrupts? 

I wanted to check various 6522 registers to see if the interrupt occurred or not AFTER the routine. I knew that not reading the correct register would cause another interrupt immediately. The idea was that SEI would stop that. But Marko explained why it wouldn't work. And, as I realized my self, it wouldn't work with a NMI at all.

> As said, it would be best if you could give a complete, but as small as possible, program code so we can see what you are doing, and tell us what you are expecting.

Not yet because I'm sure I will be accused of inventing the wheel twice again :)

Met vriendelijke groet / With kind regards, Ruud Baltissen

De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de 
geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te 
nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit 
e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken. 
Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige 
overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij 
overgebrachte virussen.

APG Groep N.V. is gevestigd te Heerlen en is ingeschreven in het 
handelsregister van de Kamer van Koophandel Limburg onder nummer 14099617

The information contained in this e-mail is confidential and may be privileged. 
It may be read, copied and used only by the intended recipient. 
If you have received it in error, please contact the sender immediately by 
return e-mail; please delete in this case the e-mail and do not disclose its 
contents to any person. We don't accept liability for any errors, omissions, 
delays of receipt or viruses in the contents of this message which arise as a 
result of e-mail transmission.

APG Groep N.V. is registered in the trade register of the Chamber 
of Commerce Limburg, The Netherlands, registration number: 14099617

       Message was sent through the cbm-hackers mailing list
Received on 2017-07-29 08:00:02

Archive generated by hypermail 2.2.0.