Assembly, programming interrupt service routines

uniquity · 11-04-2009, 11:28 PM

i'm trying to write a program which involves two user programs, one trap routine and a interrupt service routine

the first user program simply calls trap routine x26 which waits for input, then enables the interrupt bit on KBSR. once a key is pressed, the second user program is supposed to start while program waits for more input. all the second user program does is output asterisks. its supposed to keep outputting asterisks while user program 1 is waiting for input...once 5 keys are pressed the program is halted

right now, my program only takes in 5 keys and outputs them but the 2nd user program is never called upon and no asterisks are outputted.

below is the code for the trap routine, can anyone help me out and let me know why the 2nd user program is never called? p.s. x3400 is the starting address of the 2nd user program

Code:

	.ORIG	x3300

START	LD	R4, BIT		; load bit to enable KBSR
	STI	R7, ADDR	; save PC/R7 to x32FF
WAIT	LDI	R5, KBSR	; load KBSR to R5		
	BRzp	WAIT		; wait for input
	LDI	R0, KBDR	; load input to R0
	ADD	R5, R5, R4	; enable interrupt bit
	STI	R5, KBSR	; set KBSR
	LD	R7, UP2		; load starting address of UP2
	JMP	R7		; return to UP2

ADDR	.FILL	x32FF		; address to store PC
UP2	.FILL	x3400		; starting address of UP2
KBSR	.FILL	xFE00		; address of KBSR
KBDR	.FILL	xFE02		; address of KBDR
BIT	.FILL	#16384		; bit to enable ready/interrupt

	.END

oracleguy · 11-05-2009, 12:05 AM

What architecture is this for?

drhowarddrfine · 11-05-2009, 12:30 AM

It looks like ARM.

The only thing I can tell is it looks like the only chance to break out of this loop is if it receives keyboard input. So the obvious question is, are you sure you're getting keyboard data?

uniquity · 11-05-2009, 01:45 AM

i am using an lc-3 simulator for these programs.

drhowarddrfine - yes, its getting keyboard data, everything works fine in my program until you hit the JMP R7 line, which is supposed to jump it to address x3400, but it jumps instead to the interrupt service routine (x3500) without ever going to x3400 (2nd user program)

drhowarddrfine · 11-05-2009, 04:47 AM

Never heard of this simulator before. This is something you'll have a hard time finding an answer for outside your class.

11-04-2009, 11:28 PM	PM User \| #1
uniquity New Coder Join Date: Jan 2004 Location: CA Posts: 48 Thanks: 3 Thanked 0 Times in 0 Posts	Assembly, programming interrupt service routines i'm trying to write a program which involves two user programs, one trap routine and a interrupt service routine the first user program simply calls trap routine x26 which waits for input, then enables the interrupt bit on KBSR. once a key is pressed, the second user program is supposed to start while program waits for more input. all the second user program does is output asterisks. its supposed to keep outputting asterisks while user program 1 is waiting for input...once 5 keys are pressed the program is halted right now, my program only takes in 5 keys and outputs them but the 2nd user program is never called upon and no asterisks are outputted. below is the code for the trap routine, can anyone help me out and let me know why the 2nd user program is never called? p.s. x3400 is the starting address of the 2nd user program Code: .ORIG x3300 START LD R4, BIT ; load bit to enable KBSR STI R7, ADDR ; save PC/R7 to x32FF WAIT LDI R5, KBSR ; load KBSR to R5 BRzp WAIT ; wait for input LDI R0, KBDR ; load input to R0 ADD R5, R5, R4 ; enable interrupt bit STI R5, KBSR ; set KBSR LD R7, UP2 ; load starting address of UP2 JMP R7 ; return to UP2 ADDR .FILL x32FF ; address to store PC UP2 .FILL x3400 ; starting address of UP2 KBSR .FILL xFE00 ; address of KBSR KBDR .FILL xFE02 ; address of KBDR BIT .FILL #16384 ; bit to enable ready/interrupt .END

11-05-2009, 12:05 AM	PM User \| #2
oracleguy The Spaminator Join Date: Jun 2002 Location: USA Posts: 7,287 Thanks: 1 Thanked 148 Times in 145 Posts	What architecture is this for? __________________ OracleGuy My Blog "... the VP of our third biggest account started sweating bullets in our latest project status conference when Roy stood up and asserted: 'We don’t code our products for SMACKTARDS.'" - Daily Victim #564

11-05-2009, 12:30 AM	PM User \| #3
drhowarddrfine Senior Coder Join Date: Oct 2005 Posts: 1,066 Thanks: 0 Thanked 39 Times in 38 Posts	It looks like ARM. The only thing I can tell is it looks like the only chance to break out of this loop is if it receives keyboard input. So the obvious question is, are you sure you're getting keyboard data? __________________ IE8 is 11 years behind today's standards. Security experts say don't use IE. But it works in IE!

11-05-2009, 04:47 AM	PM User \| #5
drhowarddrfine Senior Coder Join Date: Oct 2005 Posts: 1,066 Thanks: 0 Thanked 39 Times in 38 Posts	Never heard of this simulator before. This is something you'll have a hard time finding an answer for outside your class. __________________ IE8 is 11 years behind today's standards. Security experts say don't use IE. But it works in IE!

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11-05-2009, 01:45 AM	PM User \| #4
uniquity New Coder Join Date: Jan 2004 Location: CA Posts: 48 Thanks: 3 Thanked 0 Times in 0 Posts	i am using an lc-3 simulator for these programs. drhowarddrfine - yes, its getting keyboard data, everything works fine in my program until you hit the JMP R7 line, which is supposed to jump it to address x3400, but it jumps instead to the interrupt service routine (x3500) without ever going to x3400 (2nd user program)