67 lines
913 B
ArmAsm
67 lines
913 B
ArmAsm
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.equ ADDR_BASE, 0xBF88
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.equ TRISB, 0x6040
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.equ PORTB, 0x6050
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.equ TRISE, 0x6100
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.equ LATE, 0x6120
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.data
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.text
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.globl main
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main:
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lui $t7, ADDR_BASE
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lw $t0, TRISB($t7)
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ori $t0, $t0, 0x000F
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sw $t0, TRISB($t7)
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lw $t0, TRISE($t7)
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andi $t0, $t0, 0xFF00
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sw $t0, TRISE($t7)
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loop:
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lw $t0, PORTB($t7)
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andi $t0, $t0, 0x000F
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move $a0, $t0
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addi $sp, $sp, -8
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sw $ra, 0($sp)
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sw $t0, 4($sp)
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jal reverse_byte
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lw $ra, 0($sp)
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lw $t0, 4($sp)
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addi $sp, $sp, 8
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or $t0, $t0, $v0
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lw $t1, LATE($t7)
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andi $t1, $t1, 0xFF00
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or $t1, $t1, $t0
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sw $t1, LATE($t7)
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j loop
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jr $ra
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reverse_byte:
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move $v0, $a0
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andi $t0, $v0, 0xF0
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srl $t0, $t0, 4
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andi $t1, $v0, 0x0F
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sll $t1, $t1, 4
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or $v0, $t0, $t1
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andi $t0, $v0, 0xCC
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srl $t0, $t0, 2
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andi $t1, $v0, 0x33
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sll $t1, $t1, 2
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or $v0, $t0, $t1
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andi $t0, $v0, 0xAA
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srl $t0, $t0, 1
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andi $t1, $v0, 0x55
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sll $t1, $t1, 1
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or $v0, $t0, $t1
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jr $ra
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