參數(shù)資料
型號: ST72C314J2
英文描述: 8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY. ADC. 16-BIT TIMERS. SPI. SCI INTERFACES
中文描述: 8位單電壓閃存微控制器。 ADC的。 16位定時(shí)器。的SPI。脊髓損傷接口
文件頁數(shù): 98/153頁
文件大?。?/td> 1988K
代理商: ST72C314J2
ST72334J/N, ST72314J/N, ST72124J
49/153
14 ON-CHIP PERIPHERALS
14.1 WATCHDOG TIMER (WDG)
14.1.1 Introduction
The Watchdog timer is used to detect the occur-
rence of a software fault, usually generated by ex-
ternal interference or by unforeseen logical condi-
tions, which causes the application program to
abandon its normal sequence. The Watchdog cir-
cuit generates an MCU reset on expiry of a pro-
grammed time period, unless the program refresh-
es the counter’s contents before the T6 bit be-
comes cleared.
14.1.2 Main Features
s
Programmable timer (64 increments of 12288
CPU cycles)
s
Programmable reset
s
Reset (if watchdog activated) after a HALT
instruction or when the T6 bit reaches zero
s
Hardware Watchdog selectable by option byte
s
Watchdog Reset indicated by status flag (in
versions with Safe Reset option only)
14.1.3 Functional Description
The counter value stored in the CR register (bits
T[6:0]), is decremented every 12,288 machine cy-
cles, and the length of the timeout period can be
programmed by the user in 64 increments.
If the watchdog is activated (the WDGA bit is set)
and when the 7-bit timer (bits T[6:0]) rolls over
from 40h to 3Fh (T6 becomes cleared), it initiates
a reset cycle pulling low the reset pin for typically
500ns.
Figure 29. Watchdog Block Diagram
RESET
WDGA
7-BIT DOWNCOUNTER
fCPU
T6
T0
CLOCK DIVIDER
WATCHDOG CONTROL REGISTER (CR)
÷12288
T1
T2
T3
T4
T5
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