----- Original Message -----
From: "David Brant" <[EMAIL PROTECTED]>
To: <sam-users@nvg.ntnu.no>
Sent: Thursday, October 30, 2008 6:48 PM
Subject: {Spam?} Re: interrupts
----- Original Message -----
From: "Simon Cooke" <[EMAIL PROTECTED]>
To: <sam-users@nvg.ntnu.no>
Sent: Thursday, October 30, 2008 6:23 PM
Subject: RE: {Spam?} Re: interrupts
IIRC, RETI is used with Mode 2 interrupts to allow for interrupt
daisy-chaining. Unless you've got hardware which uses them to vector
interrupts to a table, you really don't want to use them.
I'm curious.. why are you using Mode 2 interrupts? It's slower than the
regular ones, as it has to look up a vector table instead of just doing
an
RST &38.
(Note: I'm incredibly rusty, so I might be completely off base here).
I'm using mode 2 because my code is/can run external memory to get more
speed. Based on simcoupe I don't think there is speed problem with mode 2
it gets fired before real line 0. But what do I know!
I've just done a speed test with mode2/mode1 and there is a 0.008% speed
loss, which probably means a 8 cycles being lost each frame.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of David Brant
Sent: Thursday, October 30, 2008 10:55 AM
To: sam-users@nvg.ntnu.no
Subject: {Spam?} Re: interrupts
----- Original Message -----
From: "Simon Owen" <[EMAIL PROTECTED]>
To: <sam-users@nvg.ntnu.no>
Sent: Thursday, October 30, 2008 5:31 PM
Subject: Re: interrupts
David Brant wrote:
I'm using mode 2 interrupts when I use sim coupe's debugger I get the
normal frame interrupt and then a interrupt at line 0 point 52 (real
line not SAM coupe line) anyone know whats producing it?
It still sounds most likely to be a re-triggered interrupt, even if the
status port is &FF by the time you check it. Is your interrupt handler
fairly short? (close to the 128 cycles the interrupt is active for)
If you can e-mail me a test disk image I'll be happy to take a look.
Si
Yes its 76 cycles long, so that must be what's happening. While we are on
the subject, is there any reason to use RETI over using just RET with
interrupts.
