Câu 1: cuối kì #define _XTAL_FREQ 4000000 unsigned char i; void main(void) { ANSEL=0; ANSELH=0; TRISA1=1; TRISB=0; PORTB=0; while(1) { if(!RA1) { delay_ms(5); while(!RA1); while(1) { PORTB=1; delay_ms(500); for(i=1;i