Please help me figure out what is wrong with my implementation of the code required for this assignment. It is programmed in PLPTool 5.2. I can only get it to print "No" once, and it does it regardless of whether it is a palindrome or not. I am so close to having it working, something is just not right and I'm missing it. Thanks in advance!

In this project, you will be writing a program that receives a string of characters via the UART, checks if this string is a palindrome, and then uses a print function to print either Yes or No. A palindrome sequence of characters (typically a word or phrase) that is the same both forwards and backwards. For this project, strings will be terminated using a period (.). You may assume that a string will contain at least one character in addition to a period. You will not need to handle empty strings or strings with only a period. Your program should be able to handle multiple strings sent one after another or concatenated together. For example, the string: abba. data. should print Yes followed by No on the next line. Spaces should be ignored when checking for a palindrome and the palindrome should not be case sensitive. For example, A nut for a jar of Tuna. would be considered a palindrome.

The PLP project includes a second ASM file titled, project3_print.asm. This ASM file contains the print function used in this project. PLPTool concatenates all ASM files within a PLP project into a single location in memory (unless additional .org statements have been added to specify different location for code). No changes to project3_print.asm should be made. When called, depending on the value in register $a0, the following string will be displayed on the simulated UART devices output. If $a0 contains a zero then No will be displayed and if $a0 contains a non-zero value (e.g. one) then Yes will be displayed. The print function is called using the following instruction:

call project3_print

To use the print function, your PLP program needs to initialize the stack pointer ($sp) before performing the function call (or any other operations involving the stack pointer). For this reason, the skeleton project file includes an initialization that sets the stack pointer to 0x10fffffc (the last address of RAM).

main.asm

.org 0x10000000

# Initializations li $sp, 0x10fffffc li $s0, 0xf0000000 #UART command register li $s1, 0xf0000004 #UART status register li $s2, 0xf0000008 #UART recieve buffer # Initialize any registers you will be using here. # It can be helpful to include a comment about a register's purpose # next to an initialization at the start of the program for reference. array_ptr: # Label pointing to 100 word array .space 100 li $a0, array_ptr move $a1, $a0 UART_status: lw $t0, 0($s1) li $t1, 0b10 and $t2, $t0, $t1 beq $t2, $zero, UART_status nop lw $v0, 0($s2) sw $t1, 0($s0) check_space: li $s3, 0x20 beq $v0, $s3, UART_status nop check_uppercase: li $t5, 0x41 li $t6, 0x5A slt $t7, $t6, $v0 slt $t8, $v0, $t5 beq $t7, $t8, check_zero nop j check_period nop check_zero: beq $t7, $zero, convert_lowercase nop j check_period nop convert_lowercase: addiu $v0, $v0, 32 j store_array nop check_period: li $t9, 0x2E beq $v0, $t9, main nop j store_array nop store_array: sw $v0, 0($a1) addiu $a1, $a1, 4 j UART_status nop main: # TODO: write your primary program within this loop move $a2, $a0 li $t5, 0 push: lw $t7, 0($a2) push $t7 addiu $t5, $t5, 1 addiu $a2, $a2, 4 slt $s6, $a2, $a1 bne $s6, $zero, push nop li $t5, 0 pop: pop $t7 sw $t7, 0($a2) addiu $t5, $t5, 1 addiu $a2, $a2, 4 slt $s6, $a2, $s4 bne $s6, $zero, pop nop palindrome_check: beq $a2, $a0, one_assign nop zero_assign: li $a0, 0 call project3_print j UART_status nop one_assign: li $a0, 1 call project3_print j UART_status nop

project3_print.asm

li $a0, control_message_p3 jal libplp_uart_write_string_p3 nop control_flow_trap_p3: j control_flow_trap_p3 nop

string_yes_p3: .asciiz "Yes "

string_no_p3: .asciiz " No "

control_message_p3: .asciiz "Error: Program entered project3_print.asm due to missing control flow at the end of main.asm "

project3_print: push $ra bne $a0 $0, set_ptr_yes nop li $a0, string_no_p3 j print_string_p3 nop set_ptr_yes: li $a0, string_yes_p3

print_string_p3: jal libplp_uart_write_string_p3 nop pop $ra return

# From PLP UART Library

libplp_uart_write_p3: lui $t0, 0xf000 #uart base address libplp_uart_write_loop_p3: lw $t1, 4($t0) #get the uart status andi $t1, $t1, 0x01 #mask for the cts bit beq $t1, $zero, libplp_uart_write_loop_p3 nop sw $a0, 12($t0) #write the data to the output buffer sw $t1, 0($t0) #send the data! jr $31 nop

libplp_uart_write_string_p3: #we have a pointer to the string in a0, just loop and increment until we see a \0 move $t9, $31 #save the return address move $t8, $a0 #save the argument libplp_uart_write_string_multi_word_p3: lw $a0, 0($t8) #first 1-4 characters ori $t0, $zero, 0x00ff #reverse the word to make it big endian and $t1, $t0, $a0 #least significant byte sll $t1, $t1, 24 srl $a0, $a0, 8 and $t2, $t0, $a0 #second byte sll $t2, $t2, 16 srl $a0, $a0, 8 and $t3, $t0, $a0 #third byte sll $t3, $t3, 8 srl $a0, $a0, 8 #last byte in a0 or $a0, $t1, $a0 or $a0, $t2, $a0 or $a0, $t3, $a0 beq $a0, $zero, libplp_uart_write_string_done_p3 nop ori $t7, $zero, 4 libplp_uart_write_string_loop_p3: jal libplp_uart_write_p3 #write this byte addiu $t7, $t7, -1 srl $a0, $a0, 8 bne $a0, $zero, libplp_uart_write_string_loop_p3 nop beq $t7, $zero, libplp_uart_write_string_multi_word_p3 addiu $t8, $t8, 4 #increment for the next word libplp_uart_write_string_done_p3: jr $t9 #go home nop