Posted By
Stinaris
on 2023-12-19
05:52:08
 |  Re: Cartridge and raster interrupts
Finally got back to the C16. Wow what a busy year.
Anyway. I got my raster interrupts working by moving the interrupt routine to RAM.
So thank you everyone for your help. I have the Plus/4 Programmers Reference Manual and I've got to say it's a bit disappointing compared to the VIC and C64 versions.
Which leads me onto the next bit
While having a little play with carts I opened up my ScriptPlus cart and it as 2 ROMs.
Playing with YAPE you can set ROM C1 Low/ROM C1 High i.e. $8000-$bfff/$c000-$fcff.
It looks like you can have 2 16K Roms located at the positions above.
Using the code below I can access the lower of these and autostart my cartridge.
start sei
lda $fb ; Get current ROM bank (to provide runnability in any slots)
and #$03 ; Use our ROM in low bank only and KERNAL in high
tax
sta $fdd0,x ; Do bank selection
With my cartridge installed $fb contains 1 which looks like it relates to Bank1 but only Low.
I can't find any information that describes how, if at all possible, I can bank in the Hi/Lo regions at the same time.
I suspect it's something to do with $fddx but nothing i try banks anything in, only out :-/
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