INTA

CAS0 IR0 CAS1 IR1 CAS2 IR2 IR3 INTA IR4 IR5 INT IR6 IR7 SP/EN INTR CAS0 INTA CAS1 CAS2 INT IR0 IR1 SP/EN IR7 +5V

(2)编写主、从片初始化程序。(8分) ；初始化主片8259A MOV DX,0F000H

MOV AL，11H ICW1:11H OUT DX，AL ；ICW1 MOV DX,0F001H MOV AL，70H

OUT DX，AL ；ICW2 NOP

MOV AL，01H 00000001 OUT DX，AL ；ICW3 NOP

MOV AL，11H OUT DX，AL ；ICW4 3． (1) 画出8253的接线图；（5分）

；初始化从片8259A MOV DX,0E000H MOV AL，11H OUT DX，AL MOV DX,0E001H MOV AL，80H OUT DX，AL NOP

MOV AL，00H OUT DX，AL NOP MOV AL 01H OUT DX,AL

cs A0 A1

8253 (2)设计8253的控制程序。（5分） 计数初值=2000/[1000/(20+20)]=80=50H .MODEL TINY T1-8253 EQU 0F001H CON-8253 EQU 0F003 STACK 100 .CODE

STAR: MOVE DX,CON-8253

f=2000HZ GATE1=5v OUT1

MOVE AL,56H OUT DX,AL MOV DX,T1-8253 MOV AL,50H OUT DX,AL END STAR