Hello

I am writing a program for class to simulate a tv remote in a MIPS/SPIM enviroment. The functions of the program itself are unimportant as they worked fine before the interrupt so I left them all out. The gaol is basically to get a input from the keyboard by means of interupt, store it in $s7 and process it. The interrupt is causing my program to repeatedly spam the errors:

Exception occurred at PC=0x00400068 Bad address in data/stack read: 0x00000004

Exception occurred at PC=0x00400358 Bad address in data/stack read: 0x00000000

program starts here

.data

msg_tvworking: .asciiz "tv is working\n"

msg_sec: .asciiz "sec -- "

msg_on: .asciiz "Power On"

msg_off: .asciiz "Power Off"

msg_channel: .asciiz " Channel "

msg_volume: .asciiz " Volume "

msg_sleep: .asciiz " Sleep Timer: "

msg_dash: .asciiz "-\n"

msg_newline: .asciiz "\n"

msg_comma: .asciiz ", "

array1: .space 400 # 400 bytes of storage for 100 channels

array2: .space 400 # copy of above for sorting

var1: .word 0 # 1 if 0-9 is pressed, 0 if not

var2: .word 0 # stores number of channel (ex. 2-)

var3: .word 0 # channel timer

var4: .word 0 # 1 if s pressed once, 2 if twice, 0 if not

var5: .word 0 # sleep wait timer

var6: .word 0 # program timer

var9: .float 0.01 # for channel timings

.kdata var7: .word 10 var8: .word 11

.text .globl main main:

li $s0, 300

li $s1, 0 # channel

li $s2, 50 # volume

li $s3, 1 # power - 1:on 0:off

li $s4, 0 # sleep timer - 0:off

li $s5, 0 # temporary

li $s6, 0 # length of sleep period

li $s7, 10000 # current key press

li $t2, 0 # temp value not needed across calls

li $t4, 0

interrupt data here

mfc0 $a0, $12 ori $a0, 0xff11 mtc0 $a0, $12

lui $t0, 0xFFFF ori $a0, $0, 2 sw $a0, 0($t0)

mainloop:

# 1. get external input, and process it

# input from interupt is taken from $a2 and placed in $s7 #for processing

beq $a2, $0, next lw $s7, 4($a2) li $a2, 0

# call the process_input function here

# jal process_input

next:

# 2. check sleep timer mainloopnext1:

# 3. delay for 10ms jal delay_10ms

jal check_timers jal channel_time

# 4. print status

lw $s5, var6 addi $s5, $s5, 1 sw $s5, var6

addi $s0, $s0, -1 bne $s0, $0, mainloopnext4 li $s0, 300 jal status_print

mainloopnext4: j mainloop

li $v0,10 # exit syscall

--------------------------------------------------

status_print: seconds_stat:

power_stat:

on_stat:

off_stat:

channel_stat:

volume_stat:

sleep_stat:

j $ra

--------------------------------------------------

delay_10ms: li $t0, 6000 delay_10ms_loop: addi $t0, $t0, -1 bne $t0, $0, delay_10ms_loop jr $ra

--------------------------------------------------

check_timers: channel_press:

sleep_press:

go_back_press:

channel_check:

channel_ignore:

sleep_check:

sleep_ignore:

j $ra

------------------------------------------------

process_input: beq $s7, 112, power beq $s7, 117, channel_up beq $s7, 100, channel_down beq $s7, 108, volume_up beq $s7, 107, volume_down beq $s7, 115, sleep_init beq $s7, 118, history bgt $s7, 47, end_range jr $ra

end_range:

power:

on:

off:

channel_up:

over:

channel_down:

under:

channel_message:

channel_time:

volume_up:

volume_down:

volume_message:

sleep_init:

sleep_incr:

sleep:

sleep_reset:

history:

digit_pad_init:

digit_pad:

jr $ra

--------------------------------------------

interupt data here, followed closely from class

.ktext 0x80000180

.set noat move $k1, $at .set at

sw $v0, var7 sw $a0, var8

mfc0 $k0, $13 srl $a0, $k0, 2 andi $a0, $a0, 0x1f

bne $a0, $zero, no_io

lui $v0, 0xFFFF lw $a2, 4($v0) # keyboard data placed in $a2

no_io: mtc0 $0, $13 mfc0 $k0, $12 andi $k0, 0xfffd ori $k0, 0x11 mtc0 $k0, $12

lw $v0, var7 lw $a0, var8

.set noat move $at, $k1 .set at

eret

Thanks in advance.