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#include <avr/io.h>
#include <avr/interrupt.h>
#undef _SFR_IO8
#define _SFR_IO8(x) (x)
#undef _SFR_IO16
#define _SFR_IO16(x) (x)
.global main
main:
ldi r18, 0x00 ; we check later for other value
ldi r19, 0x00 ; we check later for other value
ldi r20, 0x00 ; we check later for other value
ldi r16, 0xff ; all pins output
out DDRB, r16 ; all pins output
ldi r16, 0x01 ; one pin on
out PORTB, r16 ; initial only 1 pin
sei ; enable global irqs
ldi r16, (1<<UDRIE) ; lets generate a usart data register empty irq
out UCSRB, r16 ; fire hardware irq, I flag is already set
cli ; but there is one more instruction to do
; and cli should prevent going to irq after the command has
; executed!
; because the irq should NOT be fired, we see the result of the next instruction
; after test finsihed
ldi r18, 0x01 ; 0x01 must be found in R10 after test
; now we do some additional tests
sei ; now the irq should be enabled again
ldi r19, 0x02 ; this command should be executed after a sei
; but the following instructions should NOT be executed
ldi r20, 0x03 ; so the old value 0x00 should be here
ret ; this will result in going back to ctors_end -> exit
.global USART_UDRE_vect
USART_UDRE_vect:
ldi r17, 0xff; ; if we run into irq, we will see 0xff
out PORTB, r17
.global stopsim
stopsim:
rjmp USART_UDRE_vect
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