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.