Okay, gang. Here's what I've got.
First up, supposing I use a BEQ, writing it as:
BEQ #0
(I believe #0 means numeric value zero, right?) Does the computer
check the last value to be changed against the value or location I list
after the BEQ command, like if I Decrement X (DCX?), or does it compare
the X, Y, and A registers all against the value after the BEQ?
I don't have the commands handy, but I recall commands that
allowed me to INCrement or DECrement things held in actual memory
locations. With this in mind, how close is this to what I need to do
for the solitaire game?
WSYNC
VBLANK
During this VBLANK, I put a couple of commands--nothing heavy. I
then VBLANK again, start the next command, etc. I do this thirty-seven
times, breaking up the commands to fit within the VBLANK times.
Next, I start drawing the screen. Assuming I can DEC a value in
memory location and compare that instead of constantly shifting the
values into and out of the X or Y registers, I do this:
LDX #192
STX LINECNT
Draw screen commands here.
DEC LINECNT
BEQ #0
JMP Two commands down
Clear all carry flags (just to make sure)
JMP Back to the draw screen commands.
Clear all carry flags
LDX #30
STX LINECNT
VBLANK
Do any extra game calculations I can here.
DEC LINECNT
BEQ #0
JMP Two commands down
Clear all carry flags
JMP back to VBLANK command
JMP back to top of all this, start the cycle over
Am I getting closer, or no?
Also, some other questions.
Erik Mooney wrote that during the first set of VBLANK commands, I
have time for 800-1000 commands. A FAQ I boosted off the 'Net says I
have time for 80-100. Did someone misplace a zero, or are both answers
correct and I'll discover how to do both with practice?
What color is produced by VBLANK? If I need extra time to
complete game calculations, like in the Columns example about a month
ago, can I start VBLANKing as soon as I draw the last part of the
screen needed, buying myself a little more time to work on things?
To save time, I'm envisioning in the mental flowchart I came up
with then starting the VBLANK after VSYNC with checking for a joystick
input. If none, it just bounces through to the screen drawing part.
If there is, if first checks what kind it is. If I put the "check what
it is" subroutines here, I should be able to just have the computer do
a subroutine when needed, and that won't tie up the processor during
the VBLANK because, if done right, only a couple of commands will be
needed and I can send the program right back to the VBLANK cycle before
the beam reaches the edge, right?
Am I getting closer, or am I getting all this royally wrong?
"We don't need no new set of standards,
"We don't need no new set of rules."
Operation Ivy
-"Take Warning"
(With apologies, I know I took that completely out of context.)
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