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Trap
Registered: Jul 2010
Posts: 222 |
Best practice IRQ recovery
Hi,
Here's a little newbie question. Sorry, I'm still learning this shit and it's really complicated :(
I have kernel off ($01=$35) and I am running IRQ's using the normal $fffe/$ffff vectors.
I want to exit from this and call a prepacked piece of code (in this case something packed with TinyCrunch).
I tried restoring the IRQ vectors and jump to the packer. However, it just hangs. I tried some other things but all gave the same result. The only thing that worked was when I did this:
sei
lda #$36
sta $01
jsr $ff81
jmp unpacker
The problem of course is that it resets the VIC which isn't really great for my situation.
So, my question:
What is the correct/proper way to exit from a part and go to the next? preferably not using kernal routines :|
Thank you.
Trap |
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Martin Piper
Registered: Nov 2007
Posts: 631 |
Tried single stepping using the debugger in Vice?
It will probably show where various IRQs happen after the CLI.
Create, or reuse, consistent IRQ disable and ACK code: https://github.com/martinpiper/C64Public/blob/master/stdlib/std..
I generally always use this to initialise to a known state: https://github.com/martinpiper/C64Public/blob/master/stdlib/Ini.. |
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Oswald
Registered: Apr 2002
Posts: 5017 |
"lda #$7f
sta CIA1InterruptControl
sta CIA2InterruptControl"
I will stick to dc0d dd0d :D letsnamealltheregisters_so_itseasyertocode NOT. |
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Martin Piper
Registered: Nov 2007
Posts: 631 |
It's easier for me to name registers and sometimes their bitfields. |
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chatGPZ
Registered: Dec 2001
Posts: 11100 |
Is this "how to make trivial code unreadable 101"? /o\ |
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Krill
Registered: Apr 2002
Posts: 2825 |
Oh come on, the registers have names already in the datasheet.
And not everybody spent years writing and analysing code with a memory monitor before using a proper assembler. =)
I'd stick to concise symbols like "CIA1_ICR", though.
And yes, using symbols instead of raw addresses and bitfields can make code more readable, especially with rarely used registers. |
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Oswald
Registered: Apr 2002
Posts: 5017 |
Quote: Oh come on, the registers have names already in the datasheet.
And not everybody spent years writing and analysing code with a memory monitor before using a proper assembler. =)
I'd stick to concise symbols like "CIA1_ICR", though.
And yes, using symbols instead of raw addresses and bitfields can make code more readable, especially with rarely used registers.
I'm sorry, for me lda $#7f sta $dc0d is more readable than lda #CIAdisableallinterrupts sta Cia2interruptcontrolregister. anyone who didnt spent years using these registers by hex values raise their hands. nobody? good :)
and btw if you code like this, and then you see your code in monitor, you will have no clue what part of your code you see. same goes for source code thats programmed as a script. |
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TWW
Registered: Jul 2009
Posts: 541 |
Best of both worlds :)
// Disable all CIA interrupts
lda #$7f
sta $dc0d
sta $dd0d
// Acknowlege any pending CIA iterrupts
lda $dc0d
lda $dd0d
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Krill
Registered: Apr 2002
Posts: 2825 |
Quoting Oswaldanyone who didnt spent years using these registers by hex values raise their hands. nobody? good :) Some people got into C-64 coding only recently.
Quote:if you code like this, and then you see your code in monitor, you will have no clue what part of your code you see. VICEmon symbol files have been invented. \=D/
Quote:same goes for source code thats programmed as a script. Please elaborate. |
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chatGPZ
Registered: Dec 2001
Posts: 11100 |
TWW: there are no pending interrupts after disabling them (or to be precise, they'd still trigger, before you can even ACK, the original handler will take care of them) |
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TWW
Registered: Jul 2009
Posts: 541 |
GPZ: This is done inside a sei-cli raster IRQ setup to ensure no accidental CIA IRQ triggers after cli'ing which may have activated between the sei and the point you actually disable them. |
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