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Z80 & 68k Assembly =>
z80 & ez80 Assembly
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qxzwasd
Newbie
Joined: 07 Apr 2009
Posts: 2
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 Posted: 06 May 2009 05:04:41 pm Post subject: |
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Hi everyone. I'm new to assembly programming, and this is a small program I wrote. It's just moving a "*" around the screen using the arrow keys. Here's the code:
Code:
.NOLIST
#INCLUDE "ti83plus.inc"
.LIST
.ORG $9D93
.DB $BB, $6D
Draw:
b_call(_ClrScrnFull)
LD A, (XPos)
LD (CurCol), A
LD A, (YPos)
LD (CurRow), A
LD A, '*'
b_call(_PutC)
KeyLoop:
b_call(_GetKey)
CP kClear
JR Z, Exit
CP kLeft
JR Z, KeyLeft
CP kRight
JR Z, KeyRight
CP kUp
JR Z, KeyUp
CP kDown
JR Z, KeyDown
JR KeyLoop
KeyLeft:
LD A, (XPos)
DEC A
LD (XPos), A
JR Draw
KeyRight:
LD A, (XPos)
INC A
LD (XPos), A
JR Draw
KeyUp:
LD A, (YPos)
DEC A
LD (YPos), A
JR Draw
KeyDown:
LD A, (YPos)
INC A
LD (YPos), A
JR Draw
Exit:
RET
XPos:
.DB 4
YPos:
.DB 8
.END
When I run it I can move it left and right, but not up and down, and when I press clear symbols start scrolling on the screen. I can press 2nd-quit to get to the homescreen, but then it says that I have no free RAM. Could somebody just look at it and see if you see any obvious mistakes? Thanks.
EDIT: And I know that you can move off the screen and that will make it act weird, but that's not the problem. It won't move up or down at all.
Last edited by Guest on 06 May 2009 05:22:49 pm; edited 1 time in total |
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benryves
Active Member
Joined: 23 Feb 2006
Posts: 564
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| Posted: 06 May 2009 05:27:05 pm Post subject: |
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qxzwasd wrote: EDIT: And I know that you can move off the screen and that will make it act weird, but that's not the problem. It won't move up or down at all. Your initial Y coordinate is 8, which is off the screen (Y is 0 to 7, X is 0 to 15). I think you have your XPos and YPos .db directives at the end of the program the wrong way around. |
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qxzwasd
Newbie
Joined: 07 Apr 2009
Posts: 2
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| Posted: 06 May 2009 05:30:00 pm Post subject: |
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benryves wrote: qxzwasd wrote: EDIT: And I know that you can move off the screen and that will make it act weird, but that's not the problem. It won't move up or down at all. Your initial Y coordinate is 8, which is off the screen (Y is 0 to 7, X is 0 to 15). I think you have your XPos and YPos .db directives at the end of the program the wrong way around.
Wow, thanks. I actually had them switched in one place, but I fixed that. I guess I had them switched everywhere. Thanks for your help, I'm surprised I didn't catch that. |
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