I am wondering how to convert an ASCII string into a value in to a single regist

Question

I am wondering how to convert an ASCII string into a value in to a single register $v0 using PLP Tool. Showing the answer of the converted value in the UART window. The for each input number, the calculator should revert to a state where it is ready to take another number as a input, or in other words resetting the PLP Tool simulation, without resetting the $v0 register value.

The full asignment details are below:

Create a program that converts an ASCII string into a value in a single register. An equals character (‘=’) will be used to indicate the end of a number. The result of your conversion should be put in register $v0. You do not need to handle checking if a character is something other than a number or an equals sign (=).
Following each number input the calculator should revert to a state where it is ready to take another number as input. In other words, manually resetting the PLPTool simulation between numbers should not be required. It should be ready and waiting for another input after processing the previous input without resetting $v0.

An working example is:

.org 0x10000000

main:
li $s0, 0xf0000000 #load UART
and $v0, $v0, $zero #set $v0 to zero using bitwise AND

#load values
li $s1, 0x30 #offset for ascii 0
li $s2, 0x39 #offset for ascii 9
li $s3, 0x45 #ascii minus sign
li $s4, 0x61 #ascii equals sign
li $s5, 0x02 #ready bit mask, ready bit compare, command clear ready bit
li $s6, 0x01 #command send bit, clear to send

start:
li $t1, 0x00 #value to send to $v0
li $a0, 0x00 #1st pass counter

I asked a similar question earlier, but didn't have good details. Thus got good but partial answer.

Explanation / Answer

.data #declaration of vars follows array: .space 11 #reserves space for a 10 elem array char: .space 2 prompt: .asciiz "Please enter 10 numbers, then press ENTER: " null: .asciiz "" space: .ascii " " newline: .asciiz " " .text #instructions follow main: la $a0, prompt #load prompt message into $a0 for syscall li $v0, 4 #load syscall to print string syscall #print prompt message j readInt #call readInt function to get user input string gets: #read multiple chars from keyboard buffer until ENTER key, #add NULL char and store into buffer pointed to by *array #passed to the subroutine la $s1, array #set base address of array to s1 loop: #start of read loop jal getc #jump to getc subroutine lb $t0, char #load the char from char buffer into t0, stripping null sb $t0, 0($s1) #store the char into the nth elem of array lb $t1, newline #load newline char into t1 beq $t0, $t1, done #end of string? jump to done addi $s1, $s1, 1 #increments base address of array j loop #jump to start of read loop getc: #read char from keyboard buffer and return ascii value li $v0, 8 #call code for read string la $a0, char #load address of char for read li $a1, 2 #length of string is 1byte char and 1byte for null syscall #store the char byte from input buffer into char jr $ra #jump-register to calling function readInt: #read string of ascii digits, store into a local variable and #convert into integer, return that int unless string contains #non-integers j gets #let s1 be top address of array, let s0 be the digitcounter done: #let s2 be the sum total addi $s1, $s1, -1 #reposition array pointer to last char before newline char la $s0, array #set base address of array to s0 for use as counter addi $s0, $s0, -1 #reposition base array to read leftmost char in string add $s2, $zero, $zero #initialize sum to 0 li $t0, 10 #set t0 to be 10, used for decimal conversion li $t3, 1 lb $t1, 0($s1) #load char from array into t1 blt $t1, 48, error #check if char is not a digit (ascii'9') addi $t1, $t1, -48 #converts t1's ascii value to dec value add $s2, $s2, $t1 #add dec value of t1 to sumtotal addi $s1, $s1, -1 #decrement array address lp: #loop for all digits preceeding the LSB mul $t3, $t3, $t0 #multiply power by 10 beq $s1, $s0, FIN #exit if beginning of string is reached lb $t1, ($s1) #load char from array into t1 blt $t1, 48, error #check if char is not a digit (ascii'9') addi $t1, $t1, -48 #converts t1's ascii value to dec value mul $t1, $t1, $t3 #t1*10^(counter) add $s2, $s2, $t1 #sumtotal=sumtotal+t1 addi $s1, $s1, -1 #decrement array address j lp #jump to start of loop error: #if non digit chars are entered, readInt returns 0 add $s2, $zero, $zero j FIN FIN: li $v0, 1 add $a0, $s2, $zero syscall li $v0, 10 #ends program syscall

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