Signetics 2650 & 2636 programming/Tutorial code - background grid
Tutorial code - Background grid
[edit | edit source]This is the code for the tutorial Background grid
 | This code block must be merged with the standard 'Hardware definitions' code before it can be assembled |
reset_vector:
bcta,un reset
interrupt_vector:
retc,un ;just in case an interrupt occurs before we disable them
reset:
lodi,r0 $20 ;initialise program status word, just to be sure!
lpsu ;inhibit interrupts, stack pointer=0
lpsl ;register bank 0, without carry, arithmetic compare
eorz r0
stra,r0 effects ;initialise the 74LS378
bsta,un InitPVI ;initialise video chip
endless:
bctr,un endless
;===================================================================
; subroutine - initialise PVI
InitPVI:
eorz r0 ;r0 = 0
lodi,r3 $CA ;set 1F00-1FC9 to 00 (most of PVI)
loop1: ;sets all colours to black, turns off sound, score 1 field at top.
stra,r0 shape1,r3-
brnr,r3 loop1
lodi,r0 $78
stra,r0 coloursback
lodi,r0 $FF
stra,r0 score12
stra,r0 score34
lodi,r3 $2D
loopIS: ;load sprite shape and coords
loda,r0 one,r3-
stra,r0 grid,r3
brnr,r3 loopIS
retc,un
one:
dw $FFFF ; 1
dw $FFFF ; 2
dw $FFFF ; 3
dw $FFFF ; 4
dw $FFFF ; 5
dw $FFFF ; 6
dw $FFFF ; 7
dw $FFFF ; 8
dw $FFFF ; 9
dw $FFFF ; 10
dw $FFFF ; 11
dw $FFFF ; 12
dw $FFFF ; 13
dw $FFFF ; 14
dw $FFFF ; 15
dw $FFFF ; 16
dw $FFFF ; 17
dw $FFFF ; 18
dw $FFFF ; 19
dw $FFFF ; 20
; EXTEND x1,2,4 EXTEND x8
; ------------- -----------------------
db $09 ; Rows 1-4 4B 4A 3 2B 2A 1
db $09 ; Rows 5-8 8B 8A 7 6B 6A 5
db $09 ; Rows 9-12 12B 12A 11 10B 10A 9
db $09 ; Rows 13-16 16B 16A 15 14B 14A 13
db $09 ; Rows 17-20 20B 20A 19 18B 18A 17