参数资料
型号: AT89C51ED2-SMSUM
厂商: Atmel
文件页数: 79/137页
文件大小: 0K
描述: IC 8051 MCU FLASH 64K 68PLCC
产品培训模块: MCU Product Line Introduction
标准包装: 304
系列: 89C
核心处理器: 8051
芯体尺寸: 8-位
速度: 60MHz
连通性: SPI,UART/USART
外围设备: POR,PWM,WDT
输入/输出数: 50
程序存储器容量: 64KB(64K x 8)
程序存储器类型: 闪存
EEPROM 大小: 2K x 8
RAM 容量: 2K x 8
电压 - 电源 (Vcc/Vdd): 2.7 V ~ 5.5 V
振荡器型: 外部
工作温度: -40°C ~ 85°C
封装/外壳: 68-PLCC
包装: 管件
配用: AT89OCD-01-ND - USB EMULATOR FOR AT8XC51 MCU
46
4235K–8051–05/08
AT89C51RD2/ED2
Figure 13-6. PCA PWM Mode
13.5
PCA Watchdog Timer
An on-board watchdog timer is available with the PCA to improve the reliability of the system
without increasing chip count. Watchdog timers are useful for systems that are susceptible to
noise, power glitches, or electrostatic discharge. Module 4 is the only PCA module that can be
programmed as a watchdog. However, this module can still be used for other modes if the
watchdog is not needed. Figure 13-4 shows a diagram of how the watchdog works. The user
pre-loads a 16-bit value in the compare registers. Just like the other compare modes, this 16-bit
value is compared to the PCA timer value. If a match is allowed to occur, an internal reset will be
generated. This will not cause the RST pin to be driven high.
In order to hold off the reset, the user has three options:
1.
Periodically change the compare value so it will never match the PCA timer.
2.
Periodically change the PCA timer value so it will never match the compare values.
3.
Disable the watchdog by clearing the WDTE bit before a match occurs and then re-
enable it.
CL
CCAPnH
CCAPnL
ECOMn
CCAPMn, n= 0 to 4
0xDA to 0xDE
CAPNn MATn TOGn PWMn ECCFn
CAPPn
8-bit Comparator
CEXn
“0”
“1”
Enable
PCA Counter/Timer
Overflow
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