03-06-2016, 01:24 AM
I've found some fundamental information about the Direct Page, which can be changed by assembly opcodes, and thought I'd make a page for critical reference info like this:
The user Synchisi also had a quote about the direct page changing in C2 based on code, so it's actually changed at times, apparently.
The stack address can also be defined as well--It's not just $100 - $1FF like in previous chipsets. Does anyone know what the stack address boundaries are?
Quote:Hatzen08
11-30-2015, 02:44 PM
RE: ASM coding - Checking battle command in use
Perhaps, can it be the direct page value? In the C2 bank, it is always zero and TDC is almost used to clear the two bytes of the A register. When the direct page is changed, it always is set back to zero afterwards.
The direct page can be different in the code in the C1 bank. You can try a TDC and check if the value returned to A is zero (two bytes). If it is not, it is the wrong value for the direct page and all opcodes related to the direct page will load the wrong value.
The user Synchisi also had a quote about the direct page changing in C2 based on code, so it's actually changed at times, apparently.
The stack address can also be defined as well--It's not just $100 - $1FF like in previous chipsets. Does anyone know what the stack address boundaries are?