132 lines
1.8 KiB
ArmAsm
132 lines
1.8 KiB
ArmAsm
#include <avr/io.h>
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#include "macro.h"
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#include "const.h"
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.data
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vertical_offset:
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.byte 0
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frame:
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.byte 0
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line:
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.byte 0
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.text
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.global main
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main:
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ldi r16, 0x30 ; port B, pin 4 and 5 as output
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sts DDRB, r16
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; set interrupt vectors at address 0x0, not bootloader
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; timing is important, see atmel datasheet
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ldi r16, (1 << IVCE)
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ldi r17, 0
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out IO(MCUCR), r16
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out IO(MCUCR), r17
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ldi r16, 0xa ; external interrupt 0 and 1, falling edge
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sts EICRA, r16
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ldi r16, 0x3 ; external interrupt 0 and 1, mask enable
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sts EIMSK, r16
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sei ; global interrupt enable
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1:
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sbi IO(PORTB), 5
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ldi r18, 0
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2:
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dec r18
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brne 2b
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cbi IO(PORTB), 5
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ldi r18, 0
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3:
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dec r18
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brne 3b
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rjmp 1b
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jmp .
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.global int_horizontal_sync
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int_horizontal_sync:
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push r31
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in r31, IO(SREG) ; status register
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push r31
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#if 0
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lds r31, vertical_offset
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cpi r31, 0
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breq enter1
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dec r31
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sts vertical_offset, r31
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jmp int_horizontal_sync_end
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enter1:
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lds r31, line
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cpi r31, 0
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breq int_horizontal_sync_end
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inc r31
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sts line, r31
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lds r31, frame
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lsr r31
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lsr r31
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breq 2f
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1:
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dec r31
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brne 1b
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#endif
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ldi r31, 140
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1:
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dec r31
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brne 1b
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sbi IO(PORTB), 4
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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cbi IO(PORTB), 4
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int_horizontal_sync_end:
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pop r31
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out IO(SREG), r31
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pop r31
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reti
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.global int_vertical_sync
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int_vertical_sync:
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push r31
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in r31, IO(SREG)
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push r31
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lds r31, frame
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inc r31
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sts frame, r31
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ldi r31, 1
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sts line, r31
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ldi r31, VERTICAL_OFFSET
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sts vertical_offset, r31
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int_vertical_sync_end:
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pop r31
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out IO(SREG), r31
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pop r31
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reti
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