Posted By
gerliczer
on 2024-02-18
09:20:41
|  Re: Need help with raster interrupt
there seems to be a lack of detailed documentation for the TED.
I cannot count how many times I recommended in this forum the Ultimate Map by SVS. It is a very good source on everything about 264 machines.
1) You answered your question in 2). Raster interrupt is used by KERNAL. It is not a surprise that the interrupt status register does not shows any interrupt event. By the time your routine gets control, interrupt requests are already acknowledged.
3) While you are operate under KERNAL control, you don't have to manipulate $FF09 in any way. Those statements are for acknowledging interrupt request when you take over the system and manage interrupts yourself. It works like read the value of $FF09, check interrupt flag, if interrupt happened write back the value to do acknowledgement, evaluate the value to see what caused the interrupt. Similarly to the C64 with register $D019 of the VIC-II.
BTW, there are many programmes here that have their sources made public. Those are good resources for learning about these machines. plus4emu and YapeSDL sources are also good reads to see and understand "what makes them tick."
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