Game & Watch: The Legend of Zelda >> Assembly
UART
參考資訊：
1. pm_pdf
2. ds_pdf
3. game-and-watch-backup
4. game-and-watch-flashloader
UART使用到的腳位為PA-2(USART2_TX)、PA-3(USART2_RX)
USART2EN=1
USART234578SEL=3(HSI Clock)
TE=1、UE=1
Baudrate計算方式如下：
Baudrate = USART_KER_CKPRES/USART_DIV = 64000000/556 = 115108 ~= 115200
TC是傳送完成旗標
傳送資料
GPIOAEN=1
MODER2=2
AFR2=7(USART2)
main.s
.equiv PORTA_BASE, 0x58020000 .equiv PORTC_BASE, 0x58020800 .equiv PORTE_BASE, 0x58021000 .equiv GPIO_MODER, 0x0000 .equiv GPIO_ODR, 0x0014 .equiv GPIO_AFRL, 0x0020 .equiv RCC_BASE, 0x58024400 .equiv RCC_AHB4ENR, 0x0140 .equiv RCC_APB4ENR, 0x0154 .equiv RCC_CDCCIP2R, 0x0054 .equiv RCC_APB1LENR, 0x0148 .equiv USART2_BASE, 0x40004400 .equiv USART_CR1, 0x0000 .equiv USART_BRR, 0x000c .equiv USART_ISR, 0x001c .equiv USART_TDR, 0x0028 .thumb .cpu cortex-m7 .syntax unified .global _start .text .org 0x0000 _start: .word 0x20020000 .word reset .org 0x0100 .thumb_func reset: ldr r0, =RCC_BASE ldr r1, [r0, #RCC_APB1LENR] orr r1, #(1 << 17) str r1, [r0, #RCC_APB1LENR] ldr r1, [r0, #RCC_AHB4ENR] orr r1, #(1 << 0) str r1, [r0, #RCC_AHB4ENR] ldr r0, =RCC_BASE ldr r1, [r0, #RCC_CDCCIP2R] bic r1, #0x07 orr r1, #0x03 str r1, [r0, #RCC_CDCCIP2R] ldr r0, =PORTA_BASE ldr r1, [r0, #GPIO_MODER] bic r1, #0xf0 orr r1, #(2 << 4) str r1, [r0, #GPIO_MODER] ldr r1, [r0, #GPIO_AFRL] bic r1, #0xf00 orr r1, #(7 << 8) str r1, [r0, #GPIO_AFRL] ldr r0, =USART2_BASE ldr r1, =0x22c str r1, [r0, #USART_BRR] ldr r1, [r0, #USART_CR1] orr r1, #0x09 str r1, [r0, #USART_CR1] ldr r0, =USART2_BASE ldr r2, =hello 1: ldr r1, [r0, #USART_ISR] tst r1, #(1 << 6) beq 1b ldrb r1, [r2] strb r1, [r0, #USART_TDR] add r2, #1 cmp r1, #0 bne 1b b . .align hello: .asciz "Hello, world!" .end
接線如下
完成
