微處理器 - Allwinner F1C100S (荔枝派Nano) - Assembly - CCU

參考資料：
http://nano.lichee.pro/
https://mangopi.org/mangopi_r

System Bus


Bus Clock Tree


Base Address


暫存器


速度

CPU速度計算公式

PLL = (24MHz*N*K)/(M*P)

N = 30
K = 1
M = 1
P = 1
PLL = (24MHz*30*1)/(1*1) = 720MHz

main.s

    .global _start
 
    .equiv CCU_BASE,  0x01c20000
    .equiv GPIO_BASE, 0x01c20800 

    .equiv PLL_CPU_CTRL_REG, 0x0000
    .equiv CPU_CLK_SRC_REG,  0x0050
   
    .equiv PE,        (0x24 * 4)
    .equiv PORT_CFG0, 0x00
    .equiv PORT_DATA, 0x10

    .arm
    .text
_start:
    .long 0xea000016
    .byte 'e', 'G', 'O', 'N', '.', 'B', 'T', '0'
    .long 0, __spl_size
    .byte 'S', 'P', 'L', 2
    .long 0, 0
    .long 0, 0, 0, 0, 0, 0, 0, 0
    .long 0, 0, 0, 0, 0, 0, 0, 0
   
_vector:
    b reset
    b .
    b .
    b .
    b .
    b .
    b .
    b .
     
reset:
    ldr r0, =CCU_BASE
    ldr r1, =(1 << 31) | (29 << 8)
    str r1, [r0, #PLL_CPU_CTRL_REG]
1:
    ldr r1, [r0, #PLL_CPU_CTRL_REG]
    tst r1, #(1 << 28)
    beq 1b
    
    ldr r0, =CCU_BASE
    ldr r1, =(3 << 16)
    str r1, [r0, #CPU_CLK_SRC_REG]

    ldr r0, =GPIO_BASE
    ldr r1, =0x00010000
    str r1, [r0, #(PE + PORT_CFG0)]
0:
    ldr r1, =0x10
    str r1, [r0, #(PE + PORT_DATA)]
    ldr r2, =100000
1:
    subs r2, #1
    bne 1b
    ldr r1, =0x00
    str r1, [r0, #(PE + PORT_DATA)]
    ldr r2, =100000
2:
    subs r2, #1
    bne 2b
    b 0b
    .end

完成