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• Declaring more than one SPIM array causes a syntax error

  - by Zack

  Below is the beginning of a chunk of SPIM code: .data a: .space 20 b: .space 20 .text set_all: sw $ra,0($sp) li $t0,0 li $t1,10 ............ Unfortunately, the second array I declare ('b') causes the SPIM interpreter to spit out: spim: (parser) syntax error on line 3 of file spim.out b: .space 20 ^ Similar code works when I only have one array -- it seems to be the second that screws it up. I've prodded at it but can't figure out what it is about that statement that makes it break. Any thoughts? Thanks for any insight.

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• MIPS (or SPIM): Loading floating point numbers...

  - by James

  Hey hey, I am working on a little mini compiler while trying to learn some MIPS here. Here's my issue: MIPS has an instruction li (load immediate) which would work like this li $5,100 which would load 100 into register 5. However, I need to load floats into registers right now and am struggling with figuring out a way to do it...since li $5,2.5 does not work. Anyone have any advice? I am working in C, I was thinking I could somehow get the integer representation of the float I am working with (i.e. so the floats binary representation == the ints binary representation) then load the "integer" into the register and treat it like a float from then on. Maybe its too late but Im stuck right now.

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• Polled I/O on MIPS

  - by Krewie

  Hello , i'm currently implementing a calculator in MIPS which uses the polled I/O method for fetching information. I put a beq $v0, 120, exit # exit if input = ('x') on the main part of the code to tell that whenever something is fetched is equal to x, it should branch the exit function. The only problem is that my code works fine with the keyboard/display simulator on MARS but i get the interrupt exception 6 on SPIM. Why is this happening and how can i help it ? //Thx in advance

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• find substring and indices in mips

  - by ccc

  im trying find out substring and first occurrence indices. but something wrong. im comparing each element of pattern array and each element of string array until pointer reach to '\0'. and if any characater found it keep in temp array. and increasing pointers +1. whats the problem. algorithm is totaly wrong ? #Note: $v0 is a symbolic name used by the assember for $2. # $a0 is a symbolic name used by the assember for $4. .data prompt_str: .asciiz "Please type a text string: " prompt_ptr: .asciiz "Please type a pattern string: " print_yes: .asciiz "Yes, there is a match." print_no: .asciiz "No, there is no match." text_str: .asciiz "Text string : " pattern_str: .asciiz "Pattern string : " print_out: .asciiz "Output to be produced :" print_dash: .asciiz "----------------------" print_index: .asciiz "Starting index :" print_msg : .asciiz "Length of longest partial match = " nl: .asciiz "\n" str : .space 81 ptr : .space 81 tmp : .space 81 .text main: la $a0, prompt_str li $v0, 4 #print_string command. syscall la $a0,str #read string li $a1,81 li $v0,8 syscall la $t0,str #move string to $t0 la $a0,prompt_ptr li $v0,4 #print pattern command syscall la $a0,ptr #read pattern li $a1,81 li $v0,8 syscall la $t1,ptr #move pattern to $t1 la $t5,tmp #move temp to $t5 lb $t2,0($t0) #pointer first element array of string lb $t3,0($t1) #pointer first element array of pattern lb $t6,0($t5) #pointer first element array of temp loop : beq $t3,$0,end_loop beq $t2,$t3,match addiu $t0,$t0,1 j loop match : move $t6,$t2 addiu $t5,$t5,1 addiu $t0,$t0,1 addiu $t1,$t1,1 j print_match print_match : la $a0,text_str #print string li $v0,4 syscall move $a0,$t0 li $v0,4 syscall la $a0,nl #print newline character li $v0,4 syscall la $a0,pattern_str #print pattern string li $v0,4 syscall move $a0,$t1 li $v0,4 syscall la $a0,nl #print newline character li $v0,4 syscall la $a0,print_out #print output line and newline character li $v0,4 syscall la $a0,nl li $v0,4 syscall la $a0,print_dash li $v0,4 syscall la $a0,print_yes li $v0,4 syscall la $a0,print_index #print starting index li $v0,4 syscall li $v0,10 syscall end_loop : li $v0,10 syscall

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• MIPS Assembler Instruction parameters

  - by Martin K.

  Hi, why does such a instruction as mul $t1, $v0 , 4 evaluates as expected. But mul $t1, 4 , $v0 results in a syntax error! I wonder why the first one works, because mul only works with registers per default, so I expect that only a solution like this will be workin li $t1, 4 # set $t1 = 4 mul $t1, $v0 , $t1 # set $t1 = 4 * n I'm using the SPIM simulator.

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• MIPS: removing non alpha-numeric characters from a string

  - by Kron

  I'm in the process of writing a program in MIPS that will determine whether or not a user entered string is a palindrome. It has three subroutines which are under construction. Here is the main block of code, subroutines to follow with relevant info: .data Buffer: .asciiz " " # 80 bytes in Buffer intro: .asciiz "Hello, please enter a string of up to 80 characters. I will then tell you if that string was a palindrome!" .text main: li $v0, 4 # print_string call number la $a0, intro # pointer to string in memory syscall li $v0, 8 #syscall code for reading string la $a0, Buffer #save read string into buffer li $a1, 80 #string is 80 bytes long syscall li $s0, 0 #i = 0 li $t0, 80 #max for i to reach la $a0, Buffer jal stripNonAlpha li $v0, 4 # print_string call number la $a0, Buffer # pointer to string in memory syscall li $s0, 0 jal findEnd jal toUpperCase li $v0, 4 # print_string call number la $a0, Buffer # pointer to string in memory syscall Firstly, it's supposed to remove all non alpha-numeric characters from the string before hand, but when it encounters a character designated for removal, all characters after that are removed. stripNonAlpha: beq $s0, $t0, stripEnd #if i = 80 end add $t4, $s0, $a0 #address of Buffer[i] in $t4 lb $s1, 0($t4) #load value of Buffer[i] addi $s0, $s0, 1 #i = i + 1 slti $t1, $s1, 48 #if ascii code is less than 48 bne $t1, $zero, strip #remove ascii character slti $t1, $s1, 58 #if ascii code is greater than 57 #and slti $t2, $s1, 65 #if ascii code is less than 65 slt $t3, $t1, $t2 bne $t3, $zero, strip #remove ascii character slti $t1, $s1, 91 #if ascii code is greater than 90 #and slti $t2, $s1, 97 #if ascii code is less than 97 slt $t3, $t1, $t2 bne $t3, $zero, strip #remove ascii character slti $t1, $s1, 123 #if ascii character is greater than 122 beq $t1, $zero, strip #remove ascii character j stripNonAlpha #go to stripNonAlpha strip: #add $t5, $s0, $a0 #address of Buffer[i] in $t5 sb $0, 0($t4) #Buffer[i] = 0 #addi $s0, $s0, 1 #i = i + 1 j stripNonAlpha #go to stripNonAlpha stripEnd: la $a0, Buffer #save modified string into buffer jr $ra #return Secondly, it is supposed to convert all lowercase characters to uppercase. toUpperCase: beq $s0, $s2, upperEnd add $t4, $s0, $a0 lb $s1, 0($t4) addi $s1, $s1, 1 slti $t1, $s1, 97 #beq $t1, $zero, upper slti $t2, $s1, 123 slt $t3, $t1, $t2 bne $t1, $zero, upper j toUpperCase upper: add $t5, $s0, $a0 addi $t6, $t6, -32 sb $t6, 0($t5) j toUpperCase upperEnd: la $a0, Buffer jr $ra The final subroutine, which checks if the string is a palindrome isn't anywhere near complete at the moment. I'm having trouble finding the end of the string because I'm not sure what PC-SPIM uses as the carriage return character. Any help is appreciated, I have the feeling most of my problems result from something silly and stupid so feel free to point out anything, no matter how small.

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• Issues with MIPS interrupt for tv remote simulator

  - by pred2040

  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.

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