dos33fsprogs/interlace_demo/pt3_write_frame.s
2019-09-13 00:59:51 -04:00

98 lines
2.0 KiB
ArmAsm

.align $100
;====================================
; mb_write_frame
;====================================
; cycle counted
; 2 + 13*(70) + 74 + 5 = 991
mb_write_frame:
ldx #0 ; set up reg count ; 2
;============
; 2
;==================================
; loop through the 14 registers
; reading the value, then write out
;==================================
mb_write_loop:
;=============================
; not r13 -- 4+5+28+26+7 = 70
; r13, not ff -- 4+5+ 4 +28+26+7 = 74
; r13 is ff -- 4+5+3+1=[61] = 74
lda AY_REGISTERS,X ; load register value ; 4
; special case R13. If it is 0xff, then don't update
; otherwise might spuriously reset the envelope settings
cpx #13 ; 2
bne mb_not_13 ; 3
; -1
cmp #$ff ; 2
bne mb_not_13 ; 3
; -1
; delay 61
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
inc TEMP ; 5
lda TEMP ; 3
jmp mb_skip_13 ; 3
mb_not_13:
; address
stx MOCK_6522_ORA1 ; put address on PA1 ; 4
stx MOCK_6522_ORA2 ; put address on PA2 ; 4
ldy #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
sty MOCK_6522_ORB1 ; latch_address on PB1 ; 4
sty MOCK_6522_ORB2 ; latch_address on PB2 ; 4
ldy #MOCK_AY_INACTIVE ; go inactive ; 2
sty MOCK_6522_ORB1 ; 4
sty MOCK_6522_ORB2 ; 4
;==========
; 28
; value
sta MOCK_6522_ORA1 ; put value on PA1 ; 4
sta MOCK_6522_ORA2 ; put value on PA2 ; 4
lda #MOCK_AY_WRITE ; ; 2
sta MOCK_6522_ORB1 ; write on PB1 ; 4
sta MOCK_6522_ORB2 ; write on PB2 ; 4
sty MOCK_6522_ORB1 ; 4
sty MOCK_6522_ORB2 ; 4
;===========
; 26
mb_no_write:
inx ; point to next register ; 2
cpx #14 ; if 14 we're done ; 2
bmi mb_write_loop ; otherwise, loop ; 3
;============
; 7
mb_skip_13:
; -1
rts ; 6
pt3_loop_smc:
.byte $0,$0