NUC972 >> Assembly
Watchdog Timer(WDT)
參考資訊：
1. pdf
2. NUC970_NonOS_BSP
3. NUC972 ARM MPU资料不是足够完善
4. 要通过硬件power on setting打开WDT，否则WDT不可用
WDT_S
解鎖順序：0x59、0x16、0x88
WDTEN、RSTEN不是Read Only
main.s
.equ GPIOB_DIR, (0xb8003000 + 0x40) .equ GPIOB_DATAOUT, (0xb8003000 + 0x44) .equ CLK_PCLKEN0, (0xb0000200 + 0x18) .equ WDT_CTL, (0xb8001800 + 0x00) .equ WDT_ALTCTL, (0xb8001800 + 0x04) .equ SYS_REGWPCTL, (0xb0000000 + 0x1fc) .equ CLK_DIVCTL8, (0xb0000200 + 0x40) .text .align 2 .global _start _start: b reset _undef: b . _swi: b . _pabort: b . _dabort: b . _reserved: b . _irq: b . _fiq: b . reset: ldr r0, =CLK_PCLKEN0 ldr r1, [r0] orr r1, #((1 << 3 ) | ( 1 << 0)) str r1, [r0] ldr r0, =CLK_DIVCTL8 ldr r1, [r0] and r1, #0xffffffcf orr r1, #0x00000020 str r1, [r0] ldr r0, =SYS_REGWPCTL ldr r1, =0x59 ldr r2, =0x16 ldr r3, =0x88 str r1, [r0] str r2, [r0] str r3, [r0] ldr r0, =WDT_CTL ldr r1, =0x78f str r1, [r0] ldr r0, =GPIOB_DIR ldr r1, =(1 << 0) str r1, [r0] loop: ldr r0, =GPIOB_DATAOUT ldr r1, =(1 << 0) str r1, [r0] ldr r4, =100000 1: nop subs r4, r4, #1 bne 1b ldr r0, =GPIOB_DATAOUT ldr r1, =~(1 << 0) str r1, [r0] ldr r4, =100000 1: nop subs r4, r4, #1 bne 1b b loop .end
P.S. 除了詭異的SYS_PWRON，還需要注意PA.3(1 = WDT is ON after power-on)腳位的設定，司徒目前PA.3是懸空，建議接到VCC，正確使用WDT
Watchdog Reset後，SDRAM資料消失，LED不再閃爍
