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.syntax unified
.cpu cortex-m0plus
.thumb
.equ IO_BANK0_BASE, 0x40014000
.equ GPIO25_STATUS, (IO_BANK0_BASE + 0x0c8)
.equ GPIO25_CTRL, (IO_BANK0_BASE + 0x0cc)
.equ SIO_BASE, 0xd0000000
.equ GPIO_OE_SET_OFST, 0x024
.equ GPIO_OUT_XOR_OFST, 0x01c
.equ ATOMIC_CLEAR, 0x3000
.type blink, %function
.global blink
blink:
ldr r1, =GPIO25_CTRL
movs r0, 5 // SIO function = 5
str r0, [r1, 0]
ldr r1, =SIO_BASE
movs r0, 1
lsls r0, r0, 25 // GPIO 25 (LED) output enable
str r0, [r1, GPIO_OE_SET_OFST]
toggle_one_second:
str r0, [r1, GPIO_OUT_XOR_OFST] // toggle GPIO 25 output level
ldr r2, =0x1fca055 // 33.3 * 10^6 (one-third of a second at 100MHz)
1: // 3 clock cycle loop
subs r2, r2, 1 // 1 clock cycle
bne 1b // 2 clock cycles when taken
b toggle_one_second
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