Code Examples from Class: Difference between revisions
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ldr sp, =stack_start ; Tell where we will place the stack. |
ldr sp, =stack_start ; Tell where we will place the stack. |
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; (It goes down (lower addresses from here.) |
; (It goes down (lower addresses from here.) |
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mov r1, #1 ; Store some numebers in some registers |
mov r1, #1 ; Store some numebers in some registers |
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mov r2, #2 |
mov r2, #2 |
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mov r3, #3 |
mov r3, #3 |
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bl subroutine |
bl subroutine |
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stop b stop |
stop b stop |
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; messes up the registers locally, |
; messes up the registers locally, |
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; then restores the registers and returns. |
; then restores the registers and returns. |
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subroutine |
subroutine |
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stmfd sp!, {r1-r2,lr} ; save used registers and the link register (r14) |
stmfd sp!, {r1-r2,lr} ; save used registers and the link register (r14) |
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mov r1,#0xffffffff ; mess up the registers |
mov r1,#0xffffffff ; mess up the registers |
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mov r2, r1 |
mov r2, r1 |
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ldmfd sp!, {r1,r2,pc} ; pop the stack and return |
ldmfd sp!, {r1,r2,pc} ; pop the stack and return |
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END |
END |
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Revision as of 13:36, 5 November 2013
- Copy to RAM
AREA Exaddress, CODE, READONLY EXPORT Reset_Handler Reset_Handler LDR R9, =list mov R7, #4 ; number in list ldr r6, =datastart loop ldr r8,[r9],#4 str r8,[r6],#4 subs r7,r7,#1 bne loop stop b stop ALIGN list DCW 0x1111, 0x2222, 0x3333, 0x4444, 0x5555 ALIGN string DCB "This is a test.",0 string2 DCB 'T','h','i' ALIGN AREA Thedata, DATA, NOINIT, READWRITE datastart SPACE 20 END
- Subroutine Example1
; First Subroutine Example
; This program demonstrates using a subroutine,
; saving registers on the stack, etc.
; Rob Frohne, 1/3/2013
stack_start EQU 0x40001000
AREA Subroutine_Example, CODE
ENTRY
Start
ldr sp, =stack_start ; Tell where we will place the stack.
; (It goes down (lower addresses from here.)
mov r1, #1 ; Store some numebers in some registers
mov r2, #2
mov r3, #3
bl subroutine
stop b stop
; This subroutine saves the registers,
; messes up the registers locally,
; then restores the registers and returns.
subroutine
stmfd sp!, {r1-r2,lr} ; save used registers and the link register (r14)
mov r1,#0xffffffff ; mess up the registers
mov r2, r1
ldmfd sp!, {r1,r2,pc} ; pop the stack and return
END