## LSU EE 4720 Computer Architecture Spring 2015 # ## LIVE Classroom example for review of MIPS: Convert int to hex string. # # This file contains the state of the code after class on Wednesday, 21 # January 2015. The program at this point is complete. .data msg: .asciiz "The value of %/s4/5d = 0x%/s4/x is %/a1/s\n" str: .align 4 .space 12 # Storage for string. values: # Table of test inputs. .word 1234 # First entry in table of test inputs. .word 0x1234 .word 0xa9 .word 0x0 .word 0xf .word 0xf00d .word -1 ############################################################################### # ## Test Code # # This code calls the hex to string routine multiple times using # data appearing above. # .text .globl __start __start: la $s2, values # Address of table of test inputs. addi $s3, $0, -1; # Value that marks end of table. MLOOP: lw $a0, 0($s2) # Load a test input from the table. la $a1, str # Set $a1 to address of storage for string. lui $t0, 0x2020 # Prepare an initial value for string. ori $t0, $t0, 0x2020 # t0 will contain four blanks. sw $t0, 0($a1) # Write string with initial value (blanks). sw $t0, 4($a1) sw $t0, 8($a1) sb $0, 11($a1) jal itos addi $a2, $0, 10 # Set length of string. lw $s4, 0($s2) # Load test input again. la $a1, str # Address of string. la $a0, msg # Address of message (printf-like format str) addi $v0, $0, 11 # Code indicating we want to run printf. syscall # Make a system call to do printf. addi $s2, $s2, 4 # Advance to next entry in table. bne $s4, $s3 MLOOP # Continue if we are not at end of table. li $v0, 10 # Exit system call. (Not used if branch taken.) syscall nop ############################################################################### # # Unsigned Integer to Hexadecimal String # itos: ## Register Usage # # CALL VALUES: # $a0: Unsigned integer, to convert. # $a1: Address of storage. # Initialized to null-terminated string of blanks. # $a2: Length of storage. # # RETURN: # There is no return register value .. # .. instead write storage at $a1 with hex representation of $a0. # # NOTE: Registers $a0-$a4 and $t0-$t7 can be modified. # NOTE: 'a' = 97, 'z' = 122, 'a' - 'A' = 32 # NOTE: '0' = 48 = 0x30 add $t6, $a1, $a2 LOOP: andi $t3, $a0, 0xf slti $t4, $t3, 10 bne $t4, $0 SOMEWHERE addi $t5, $t3, 48 IS_A_LETTER: addi $t5, $t3, 87 SOMEWHERE: addi $t6, $t6, -1 sb $t5, 0($t6) srl $a0, $a0, 4 bne $a0, $0 LOOP nop DONE: jr $ra nop