Computer system (1) Experiment 5 interrupt experiment

Experimental purpose

Show how to make the input and output suspend and resume a running program by executing the interrupt handler. The restored program is like nothing happened in the middle. This experiment uses the keyboard as input to interrupt the running program.

Experiment contents and requirements

1. Write user program: the program outputs two different lines of "ICS" at continuous intervals

2. Write the keyboard interrupt processing program: the program simply prints the characters before the user's enter (x0A) 10 times at a time.

Write the operating system enabling code: initialize R6 to x3000, indicating an empty stack; Provide the address of the interrupt handler; Put IE position 1 of KBST

Experimental steps

1. Write the user program code according to the experimental requirements

(1) Enables the user program to output two different lines of "ICS" at continuous intervals

Figure 1 Two consecutive lines of different "ICS"

(2) Embedding the counting subroutine into the main program

Figure II subroutine

2. Write interrupt processing program according to the experimental requirements

Figure III Interrupt program code 1

Figure IV Interrupt program code 2

3. Write operating system enabling code
Initialize R6 to x3000, the starting address of the interrupt vector table is X0100, and the starting address of the keyboard interrupt handler is X80. Provide the address of the interrupt handler and set the IE position of KBSR to 1

Figure v Operating system enable code

4. Run code
Put the two sections of program code into LC3 simulator to run, enter a string of characters and press enter.

Figure VI The running state before the interrupt is not executed

Figure VII Enter the character "r" before carriage return

Figure VIII Enter the character "8" before carriage return

Program code and notes

Main program code:
	.ORIG	x3000
;The starting address of the interrupt vector table is X0100，The start address of the keyboard interrupt handler is X0180,hold x2000 Save to x0180
;initialize the stack pointer
;set up the keyboard interrupt vector table entry
	LD	R0,INTERRUPT
	LD	R1,KEYBOARD
	STR	R0,R1,#0
;enable keyboard interrupts
;hold KBSR of IE(Interrupt Enable) Position 1, interrupt enable
	LD	R0,KBSR1
	LD	R1,SETKBSRIE
	STR	R1,R0,#0
	LD	R6,START
;Main program code
;start of actual user program to print ICS checkerboard
OUTPUT	LEA	R0,ODD
	TRAP	x22
	LD	R0,NEWLINE
	TRAP	x21
	JSR	DELAY	
	LEA	R0,EVEN
	TRAP	x22
	JSR	DELAY
	LD	R0,NEWLINE
	TRAP	x21	
	BRnzp	OUTPUT
STOP	HALT

;Main program data area
ODD	.STRINGZ	"ICS     ICS     ICS     ICS     ICS     ICS"
EVEN	.STRINGZ	"    ICS     ICS     ICS     ICS     ICS"
NEWLINE	.FILL		x000A
START	.FILL		x3000
KEYBOARD	.FILL	x0180
INTERRUPT	.FILL	x2000
KBSR1		.FILL	xFE00
SETKBSRIE	.FILL	x4000;And operation, extended to 16 bits
;Subroutine code
DELAY	ST	R1,SAVER1
	LD	R1,COUNT
REP	ADD	R1,R1,#-1
	BRp	REP
	LD	R1,SAVER1
	RET

;Subroutine data area
COUNT	.FILL	#2500
SAVER1	.BLKW	1

	.END


Interrupt program code:
	.ORIG	x2000
;the code
;R2 Used to store output times
	ST	R0,SAVER0
	ST	R1,SAVER1
	ST	R2,SAVER2
	ST	R3,SAVER3
	ST	R4,SAVER4
	AND	R2,R2,#0
	ADD	R2,R2,#10
;Interrupt program code (by polling)
INPUT	LDI	R3,KBSR
	BRzp	INPUT
	LDI	R0,KBDR
OUTPUT	LDI	R3,DSR
	BRzp	OUTPUT
;Determine whether it is enter
	AND	R4,R4,#0
	ADD	R4,R4,#-10
	ADD	R4,R4,R0
	BRz	CIRCLE
	ST	R0,LIN	
	BRnzp	INPUT
;Cycle output 10 times
CIRCLE	ADD	R2,R2,#0
	BRz	STOP
	ADD	R2,R2,#-1
	LD	R0,LIN
	STI	R0,DDR
	BRnzp	CIRCLE
;
STOP	LD	R0,SAVER0
	LD	R1,SAVER1
	LD	R2,SAVER2
	LD	R3,SAVER3	
	LD	R4,SAVER4
	
	RTI
	HALT

;Interrupt program data area buffer space as required
KBSR	.FILL	xFE00
KBDR	.FILL	xFE02
DSR	.FILL	xFE04
DDR	.FILL	xFE06
SAVER0	.BLKW	1
SAVER1	.BLKW	1
SAVER2	.BLKW	1
SAVER3	.BLKW	1
SAVER4	.BLKW	1
LIN	.BLKW	1
	.END

summary

I / O suspends and resumes a running program by executing an interrupt handler. The restored program is like nothing happened in the middle. The use of interrupt program can make the computer program more flexible.