mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-22 14:33:51 +00:00
26 lines
603 B
PHP
26 lines
603 B
PHP
|
|
; SetHorizPos - Sets the horizontal position of an object.
|
|
; The X register contains the index of the desired object:
|
|
; X=0: player 0
|
|
; X=1: player 1
|
|
; X=2: missile 0
|
|
; X=3: missile 1
|
|
; X=4: ball
|
|
; NOTE: This version of the routine does a NEWLINE before executing.
|
|
; It does NOT do a HMOVE and HCLR.
|
|
SetHorizPos subroutine
|
|
sec ; set carry flag
|
|
sta WSYNC ; start a new line
|
|
.DivideLoop
|
|
sbc #15 ; subtract 15
|
|
bcs .DivideLoop ; branch until negative
|
|
eor #7 ; calculate fine offset
|
|
asl
|
|
asl
|
|
asl
|
|
asl
|
|
sta HMP0,x ; set fine offset
|
|
sta RESP0,x ; fix coarse position
|
|
rts ; return to caller
|
|
|