60 lines
770 B
ArmAsm
60 lines
770 B
ArmAsm
# delay.s
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# Trevor Barnes
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# CE2801-031
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# Description: A file for handling delay routines
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.syntax unified
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.cpu cortex-m4
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.thumb
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.section .text
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.global delay_ms
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# A subroutine to create a delay of a certain number of milliseconds
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# Input:
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# r0: Length of delay (ms)
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delay_ms:
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push {r1,r2,r3,lr}
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mov r3,r0
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ms_delay:
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# 250 iterations = 1/16 of a millisecond
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mov r2, #0x10
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# Loop 16 times
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1:
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# 250
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mov r1, #0xFA
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# Loop 250 times
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2:
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sub r1, #1
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cmp r1, #0
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bne 2b
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sub r2, #1
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cmp r2, #0
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bne 1b
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sub r0, #1
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cmp r0, #0
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bne ms_delay
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mov r0,r3
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pop {r1,r2,r3,pc}
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.global lcd_delay
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# about r1 mircoseonds
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lcd_delay:
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# stack
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push {lr}
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lsl r1, r1, #3
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1:
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sub r1, r1, #1
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cmp r1, #0
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bne 1b
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# return
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pop {pc}
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