标题: 编程时的配置字设置 [打印本页] 作者: winnie 时间: 2009-5-20 17:39 标题: 编程时的配置字设置 CP1 and CP0 = Code Protection
DEBUG = In-Circuit Debugger Mode
WRT = Flash Program Memory Write Enable
CPD = Data EE Memory Code Protection
LVP = Low Voltage In-Circuit Serial Programming Enable
BODEN = Brown-Out Reset Enable bit
PWRTE = Power-up timer Enable bit
WDTE = Watchdog timer Enable bit
FOSC1 and FOSC0 = Oscillator Selection bits
Mode Range
XT 0.1 - 4MHz
LP 5 - 200KHz
RC / EXTRC DC - 4MHz
IntRC Fixed 4MHz
HS 4 - 20MHz
XT = XTAL = Standard Crystal Mode
LP = Low Power
RC / ExtRC = External RC
IntRC = Internal Fixed 4MHz Resistor /Capacitor clock
HS = High Speed
Other oscillator modes may exist - check the device datasheet
Typically the timeout period for the Watchdog Timer is 18ms,
Another feature enabled through the configuration bits is the Brown-Out Reset or
BOR. The function of Brown-Out Reset is to reset the CPU when VDD drops below
VBOR, this is typically at 4 volts.
The BOR will hold the device in reset for as long as VDD remains below VBOR.
When VDD rises above VBOR, the device is held in reset for additional time by the
PoWeR-up Timer (PWRT).
If VDD should drop below VBOR at anytime, the BOR will then restart the process
again.
The PWRT allows VDD to rise to an acceptable level to prevent ambiguous operation
Operates on an internal RC oscillator
PWRT is always be enabled when BOR is enabled
It operates on an internal RC oscillator that provides a nominal 72ms delay.
Allows PIC16F87X programming at Logic Level Signals, VPP of 13 Volts not required.
LVP is enabled from the factory, turn off if not used.
When LVP enabled RB3 is dedicated to LVP, and is not available for firmware use.
Raising RB3 to VDD and then MCLR to VDD will enter programming mode.
High voltage programming is still available.