参数资料
型号: UPD78F9212CS-CAB-A
厂商: Renesas Electronics America
文件页数: 61/175页
文件大小: 0K
描述: MCU 8BIT 4KB FLASH 16PIN
标准包装: 400
系列: 78K0S/Kx1+
核心处理器: 78K0S
芯体尺寸: 8-位
速度: 10MHz
外围设备: LVD,POR,PWM,WDT
输入/输出数: 13
程序存储器容量: 4KB(4K x 8)
程序存储器类型: 闪存
RAM 容量: 128 x 8
电压 - 电源 (Vcc/Vdd): 2 V ~ 5.5 V
数据转换器: A/D 4x10b
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 16-DIP(0.300",7.62mm)
包装: 托盘
CHAPTER 8 WATCHDOG TIMER
User’s Manual U16994EJ6V0UD
151
8.4
Operation of Watchdog Timer
8.4.1
Watchdog timer operation when “low-speed internal oscillator cannot be stopped” is selected by
option byte
The operation clock of watchdog timer is fixed to low-speed internal oscillation clock.
After reset is released, operation is started at the maximum cycle (bits 2, 1, and 0 (WDCS2, WDCS1, WDCS0) of
the watchdog timer mode register (WDTM) = 1, 1, 1). The watchdog timer operation cannot be stopped.
The following shows the watchdog timer operation after reset release.
1.
The status after reset release is as follows.
Operation clock: Low-speed internal oscillation clock
Cycle: 218/fRL (546.13 ms: At operation with fRL = 480 kHz (MAX.))
Counting starts
2.
The following should be set in the watchdog timer mode register (WDTM) by an 8-bit memory manipulation
instruction
Notes 1, 2.
Cycle: Set using bits 2 to 0 (WDCS2 to WDCS0)
3.
After the above procedures are executed, writing ACH to WDTE clears the count to 0, enabling recounting.
Notes 1.
The operation clock (low-speed internal oscillation clock) cannot be changed. If any value is written to
bits 3 and 4 (WDCS3, WDCS4) of WDTM, it is ignored.
2.
As soon as WDTM is written, the counter of the watchdog timer is cleared.
Caution
In this mode, operation of the watchdog timer cannot be stopped even during STOP instruction
execution. For 8-bit timer H1 (TMH1), a division of the low-speed internal oscillation clock can be
selected as the count source, so clear the watchdog timer using the interrupt request of TMH1
before the watchdog timer overflows after STOP instruction execution. If this processing is not
performed, an internal reset signal is generated when the watchdog timer overflows after STOP
instruction execution.
A status transition diagram is shown below
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