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|
.file "vga.S"
.data
.align 2
.globl LineCount
LineCount: .word 0
.text
.align 2
.globl Timer0IntHandler
.type Timer0IntHandler, %function
Timer0IntHandler:
@ horizontal timing
@ hfp 40 (1-40)
@ hsp 128 (41-168)
@ hbp 88 (169-256)
@ hpx 800 (257-1056)
@ total = 1056
@ vertical timing
@ vsp 4 (1-4)
@ vbp 23 (5-27)
@ vln 600 (28-627)
@ vfp 1 (628)
@ total = 628
@ *********
@ ** hfp ** [40 cycles]
@ *********
@ prologue [3 cycles]
push {r3, lr}
@ save regs [7 cycles]
push {r1, r2, r3, r4, r5, r6}
@ clear interrupt timer [5 cycles]
mov r1, #1 @ TIMER_TIMA_TIMEOUT
ldr r0, =0x40030000 @ TIMER0_BASE
str r1, [r0, #0x24] @ *(TIMER0_BASE + TIMER_O_ICR) = TIMER_TIMA_TIMEOUT
@ ptr to GPIO_PORTB_BASE in r0 [3 cycles]
@ (this will be persisted)
ldr r0, =0x40005000 @ GPIO_PORTB_BASE
nop
@ ptr to GPIO_PORTB_BASE in r1 [3 cycles]
@ (this will be persisted)
ldr r1, =0x40024000 @ GPIO_PORTE_BASE
nop
@ ptr to line counter [3 cycles]
@ (this will be persisted)
ldr r2, =LineCount
nop
@ waste cycles [16 cycles]
mov r3, #0
loop_0: @ {3*4-1=11 cycles}
add r3, #1
cmp r3, #3
bne loop_0 @2
@ hsync setup [4 cycles]
ldrb r3,[r0]
mov r4, #0xfd
and r3, r4
@ *********
@ ** hsp ** [128 cycles]
@ *********
@ set hsync low [2 cycles]
str r3, [r0] @ GPIO_PIN_1 clear
@ reset line counter [8 cycles]
ldr r4, =629
cmp r3, r4
beq .Lline_reset
nop
nop
b .Lno_reset
.Lline_reset:
mov r3, #0
str r3, [r2]
.Lno_reset:
@ inc line counter [5 cycles]
ldr r3, [r2]
add r3, #1
str r3, [r2]
@ vsync on at line 1 [9 cycles]
cmp r3, #1 @ now at start of vsp
beq .Lvsync_on
nop
nop
nop
nop
nop
b .Lcont_0
.Lvsync_on: @ {6 cycles}
ldrb r3,[r0]
mov r4, #0xfe
and r3, r4
str r3, [r0] @ GPIO_PIN_0 clear
.Lcont_0:
@ vsync off at line 5 [11 cycles]
ldr r3, [r2]
cmp r3, #5
beq .Lvsync_off
nop
nop
nop
nop
nop
b .Lcont_1
.Lvsync_off: @ {6 cycles}
ldrb r3,[r0]
mov r4, #1
orr r3, r4
str r3, [r0] @ GPIO_PIN_0 set
.Lcont_1:
@ activate pixels on line 28 [6 cycles]
ldr r3, [r2]
cmp r3, #28
beq .Lactivate_px
b .Lcont_2
.Lactivate_px: @ {1 cycle}
mov r6, #1
.Lcont_2:
@ deactivate pixels on line 628 [7 cycles]
ldr r3, [r2]
ldr r4, =628
cmp r3, r4
beq .Ldeactivate_px
b .Lcont_3
.Ldeactivate_px: @ {1 cycle}
mov r6, #0
.Lcont_3:
@ waste cycles [74 cycles]
mov r0, #0
.Lwasteloop_1: @ {18*4-1=71 cycles}
add r0, #1
cmp r0, #14
bne .Lwasteloop_1 @2
nop
nop
@ hsync off [6 cycles]
ldrb r3,[r0]
mov r4, #2
orr r3, r4 @ GPIO_PIN_1 set
str r3, [r0]
@ *********
@ ** hbp ** [88 cycles]
@ *********
@ exit on vblank [3 cycles]
cmp r6, #0
beq end
nop
@ waste cycles [83 cycles]
mov r3, #0
.Lwasteloop_2: @ {20*4-1=79 cycles}
add r3, #1
cmp r3, #19
bne .Lwasteloop_2
nop
nop
nop
@ set up color counter [1 cycle]
mov r4, #0
@ set initial rgb [1 cycle]
mov r3, #0
@ *********
@ ** hpx ** [800 cycles]
@ *********
@ output pattern [800 cycles]
.Lcolor_loop: @ {100*8-1=799}
str r3, [r1]
add r3, #1
add r4, #1
cmp r4, #100
nop
bne .Lcolor_loop
nop
@ *********
@ horizontal blanking
mov r3, #0
str r3, [r1]
end:
@ restore regs [7 cycles]
pop {r1, r2, r3, r4, r5, r6}
@ return from interrupt [4 cycles]
pop {r3, pc}
.word 0x40030000 @addmi r0, r3, r0
|
