Memory Model¶

varm has 1 MB addressable memory.

Section	Start Address
.text	0x20
.data	0x10000
Stack	0x100000 (grows down)

.text (Code)¶

Executable instructions. Each instruction is 4 bytes.

.text
mov r0, #42

.data (Data)¶

Initialized variables.

.data
msg:    .byte 'H', 'e', 'l', 'l', 'o'
value:  .word 42
buffer: .space 16

Directives: .byte, .word, .space

Memory Access¶

Load/Store instructions:

ldr r0, [r1]           ; r0 = *r1
ldr r2, [r3, #8]       ; r2 = *(r3 + 8)
ldr r4, =label         ; r4 = address of label
str r0, [r1]           ; *r1 = r0

Array indexing:

ldr r0, [r2, r3, LSL #2]  ; r0 = *(r2 + r3*4)

Stack¶

Grows downward from 0x100000.

push {r0}   ; sp -= 4, *sp = r0
pop {r1}    ; r1 = *sp, sp += 4