mirror of https://github.com/hsoft/collapseos.git
43 lines
835 B
NASM
43 lines
835 B
NASM
; REGISTER USAGE
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;
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; R1: overflow counter
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; R16: tmp stuff
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.inc "avr.h"
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.inc "tn254585.h"
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.inc "tn45.h"
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main:
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ldi r16, RAMEND&0xff
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out SPL, r16
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ldi r16, RAMEND}8
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out SPH, r16
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sbi DDRB, 0
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cbi PORTB, 0
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; To have a blinking delay that's visible, we have to prescale a lot.
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; The maximum prescaler is 1024, which makes our TCNT0 increase
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; 976 times per second, which means that it overflows 4 times per
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; second.
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in r16, TCCR0B
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ori r16, 0x05 ; CS00 + CS02 = 1024 prescaler
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out TCCR0B, r16
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clr r1
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loop:
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in r16, TIFR ; TIFR0
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sbrc r16, 1 ; is TOV0 flag clear?
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rcall toggle
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rjmp loop
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toggle:
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ldi r16, 0b00000010 ; TOV0
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out TIFR, R16
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inc r1
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cbi PORTB, 0
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sbrs r1, 1 ; if LED is on
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sbi PORTB, 0
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ret
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