sendchar.s

视频叠加处理源代码,用于在模拟视频信号上叠加字符信号

#include <avr/io.h>

.section .text
.global  test
.global  send_bchar
.global  send_hchar
.global  send_lchar
.global  send_echar


test:
push r16
push r17
push r18
push r19
push r20
push r21
mov r16,r24
ldi  r17,0x8
rcall send_bchar
goone_do:
  rol  r16
  brcs send_1char
  rcall send_lchar
  rjmp goon_send
send_1char:
  rcall send_hchar
  nop
goon_send:
  dec  r17
  cp   r17,0
  brne goone_do
rcall send_echar
pop r21
pop r20
pop r19
pop r18
pop r17
pop r16
ret
send_bchar:
ldi r18,0xfd
out PORTB,r18
rcall delay1us
ldi r18,0xff
out PORTB,r18
rcall delay1us
ret      
send_hchar:
ldi r18,0xff
out PORTB,r18
rcall delay1us
ldi r18,0xfd
out PORTB,r18
rcall delay1us
ret
send_lchar:
ldi r18,0xfd
out PORTB,r18
rcall delay1us
ldi r18,0xff
out PORTB,r18
rcall delay1us
ret
send_echar:
ldi r18,0xfd
out PORTB,r18
rcall delay1us
ret      



delay1us:
nop
nop
nop
nop
nop
nop
nop
nop
nop
ret