2440时钟体系，12MHz的晶振
6410时钟体系，12MHz的晶振
210时钟体系，24MHz晶振
时钟初始化：1、设置locktime 2、设置分频系数 4、设置CPU到异步工作模式 3、设置fclk
.text
.global _start
_start:
b reset
ldr pc, _undefined_instruction
ldr pc, _software_interrupt
ldr pc, _prefetch_abort
ldr pc, _data_abort
ldr pc, _not_used
ldr pc, _irq
ldr pc, _fiq
_undefined_instruction: .word undefined_instruction
_software_interrupt:.word software_interrupt
_prefetch_abort:.word prefetch_abort
_data_abort:.word data_abort
_not_used:.word not_used
_irq:.word irq
_fiq:.word reset
undefined_instruction:
nop
software_interrupt:
nop
prefetch_abort:
nop
data_abort:
nop
not_used:
nop
irq:
nop
fiq:
nop
reset:
bl set_svc
bl disable_watchdog
bl disable_interrupt
bl disable_mmu
bl clock_init
bl light_led
set_svc:
mrs r0, cpsr
bic r0, r0, #0x1f
orr r0, r0, #0xd3
msr cpsr, r0
mov pc, lr
#define pwTCON 0x53000000
disable_watchdog:
ldr r0, =pwTCON
mov r1, #0x0
str r1, [r0]
mov pc, lr
disable_interrupt:
mvn r1, #0x0
ldr r0, =0x4a000008
str r1,[r0]
mov pc, lr
disable_mmu:
mcr p15,0,r0,c7,c7,0
mrc p15,0,r0,c1,c0,0
bic r0,r0,#0x00000007
mcr p15,0,r0,c1,c0,0
mov pc, lr
#define GPBCON 0x56000010
#define GPBDAT 0x56000014
light_led:
ldr r0, =GPBCON
ldr r1, =0x15400
str r1,[r0]
ldr r0, =GPBDAT
ldr r1, =0x6bf
str r1, [r0]
mov pc, lr
#define CLKDIVN 0x4c000014
#define MPLLCON 0x4c000008
#define MPLL_405MHZ ((127<<12)|(2<<4)|(1<<0))
clock_init:
ldr r0, =CLKDIVN
mov r1, #0x5
str r1, [r0]
mrc p15,0,r0,c1,c0,0
orr r0,r0,#0xc0000000
mcr p15,0,r0,c1,c0,0
ldr r0, =MPLLCON
ldr r1, =MPLL_405MHZ
str r1, [r0]
mov pc, lr
黄色部分就是时钟初始化，中间一段绿色的是HDIVN不是0的时候，CPU要设置成异步模式，看下面这个
但是在6410里面，设置成异步模式看这个寄存器
第7位设置是否为异步模式，所谓代码里要用bic来清除。第六位是设置是否用PLL之后产生的时钟来提供时钟源
就这图中的这个
代码如下
.text
.global _start
_start:
b reset
ldr pc, _undefined_instruction
ldr pc, _software_interrupt
ldr pc, _prefetch_abort
ldr pc, _data_abort
ldr pc, _not_used
ldr pc, _irq
ldr pc, _fiq
_undefined_instruction: .word undefined_instruction
_software_interrupt:.word software_interrupt
_prefetch_abort:.word prefetch_abort
_data_abort:.word data_abort
_not_used:.word not_used
_irq:.word irq
_fiq:.word reset
undefined_instruction:
nop
software_interrupt:
nop
prefetch_abort:
nop
data_abort:
nop
not_used:
nop
irq:
nop
fiq:
nop
reset:
bl set_svc
bl set_peri_port
bl disable_watchdog
bl disable_interrupt
bl disable_mmu
bl clock_init
bl light_led
set_svc:
mrs r0, cpsr
bic r0, r0, #0x1f
orr r0, r0, #0xd3
msr cpsr, r0
mov pc, lr
set_peri_port:
ldr r0,=0x70000000
orr r0,r0,#0x13
mcr p15,0,r0,c15,c2,4
mov pc,lr
#define pwTCON 0x7e004000
disable_watchdog:
ldr r0, =pwTCON
mov r1, #0x0
str r1, [r0]
mov pc, lr
disable_interrupt:
mvn r1, #0x0
ldr r0, =0x71200014
str r1,[r0]
mov pc, lr
ldr r0, =0x71300014
str r1, [r0]
mov pc, lr
disable_mmu:
mcr p15,0,r0,c7,c7,0
mrc p15,0,r0,c1,c0,0
bic r0,r0,#0x00000007
mcr p15,0,r0,c1,c0,0
mov pc, lr
#define CLK_DIV0 0X7e00f020
#define OTHERS 0x7e00f900
#define MPLLCON 0x7e00f010
#define APLLCON 0x7e00f0c0
#define CLK_SRC 0x7e00f01c
#define PLL_VAL ((1<<31)|(266<<16)|(3<<8)|(1<<0))
#define DIV_VAL ((0x0<<0)|(0x1<<9)|(0x1<<8)|(0x3<<12))
clock_init:
ldr r0, =CLK_DIV0
ldr r1, =DIV_VAL
str r1, [r0]
ldr r0, = OTHERS
ldr r1, [r0]
bic r1, r1, #0xc0
str r1, [r0]
ldr r0, =MPLLCON
ldr r1, =PLL_VAL
str r1,[r0]
ldr r0, =CLK_SRC
mov r1, #0x3
str r1, [r0]
mov pc, lr
#define GPBCON 0x7f008820
#define GPBDAT 0x7f008804
light_led:
ldr r0, =GPBCON
ldr r1, =0x1111
str r1,[r0]
ldr r0, =GPBDAT
ldr r1, =0xe
str r1, [r0]
mov pc, lr
黄色部分就是设置时钟的，能看懂手册，就能写代码。
原文地址：https://www.cnblogs.com/sanshijvshi/p/8353657.html
时间： 2024-10-12 12:28:25