LPC2300系列的启动代码是不是已经自动锁存了PLL？程序里面不需要自己写代码锁定pLL了？
小弟使用Keil uVision4，里面有LPC2300的启动代码，下面是有关时钟和PLL的一段代码：
; Clock Setup ------------------------------------------------------------------
IF (:LNOT:(:DEF:NO_CLOCK_SETUP)):LAND:(CLOCK_SETUP != 0)
LDR R0, =SCB_BASE
MOV R1, #0xAA
MOV R2, #0x55
; Configure and Enable PLL
LDR R3, =SCS_Val ; Enable main oscillator
STR R3, [R0, #SCS_OFS]
IF (SCS_Val:AND:OSCEN) != 0
OSC_Loop LDR R3, [R0, #SCS_OFS] ; Wait for main osc stabilize
ANDS R3, R3, #OSCSTAT
BEQ OSC_Loop
ENDIF
LDR R3, =CLKSRCSEL_Val ; Select PLL source clock
STR R3, [R0, #CLKSRCSEL_OFS]
LDR R3, =PLLCFG_Val
STR R3, [R0, #PLLCFG_OFS]
STR R1, [R0, #PLLFEED_OFS]
STR R2, [R0, #PLLFEED_OFS]
MOV R3, #PLLCON_PLLE
STR R3, [R0, #PLLCON_OFS]
STR R1, [R0, #PLLFEED_OFS]
STR R2, [R0, #PLLFEED_OFS]
IF (CLKSRCSEL_Val:AND:3) != 2
; Wait until PLL Locked (if source is not RTC oscillator)
PLL_Loop LDR R3, [R0, #PLLSTAT_OFS]
ANDS R3, R3, #PLLSTAT_PLOCK
BEQ PLL_Loop
ELSE
; Wait at least 200 cycles (if source is RTC oscillator)
MOV R3, #(200/4)
PLL_Loop SUBS R3, R3, #1
BNE PLL_Loop
ENDIF
M_N_Lock LDR R3, [R0, #PLLSTAT_OFS]
LDR R4, =(PLLSTAT_M:OR:PLLSTAT_N)
AND R3, R3, R4
LDR R4, =PLLCFG_Val
EORS R3, R3, R4
BNE M_N_Lock
-----------------------------------------
运行以后，不做任何程序，发现PLLSTAT寄存器=0x0700000B
(原文件名:QQ截图未命名.jpg)
这时候24 25 26三位已经是1了。
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我想请教各位高手，是不是不用自己写代码锁定PLL了？
谢谢 |
发表于 2010-8-22 11:03:42
楼主