参数资料
型号: C8051F002R
厂商: Silicon Laboratories Inc
文件页数: 168/171页
文件大小: 0K
描述: IC 8051 MCU 32K FLASH 32LQFP
标准包装: 1
系列: C8051F00x
核心处理器: 8051
芯体尺寸: 8-位
速度: 20MHz
连通性: SMBus(2 线/I²C),SPI,UART/USART
外围设备: 欠压检测/复位,POR,PWM,温度传感器,WDT
输入/输出数: 8
程序存储器容量: 32KB(32K x 8)
程序存储器类型: 闪存
RAM 容量: 256 x 8
电压 - 电源 (Vcc/Vdd): 2.7 V ~ 3.6 V
数据转换器: A/D 4x12b; D/A 2x12b
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 32-LQFP
包装: 剪切带 (CT)
其它名称: 336-1002-1
C8051F000/1/2/5/6/7
C8051F010/1/2/5/6/7
13.8.1. Watchdog Usage
The WDT consists of a 21-bit timer running from the programmed system clock. The timer measures the period
between specific writes to its control register.
If this period exceeds the programmed limit, a WDT reset is
generated. The WDT can be enabled and disabled as needed in software, or can be permanently enabled if desired.
Watchdog features are controlled via the Watchdog Timer Control Register (WDTCN) shown in Figure 13.3.
Enable/Reset WDT
The watchdog timer is both enabled and the countdown restarted by writing 0xA5 to the WDTCN register. The
user’s application software should include periodic writes of 0xA5 to WDTCN as needed to prevent a watchdog
timer overflow. The WDT is enabled and restarted as a result of any system reset.
Disable WDT
Writing 0xDE followed by 0xAD to the WDTCN register disables the WDT.
The following code segment
illustrates disabling the WDT.
CLR
EA
; disable all interrupts
MOV
WDTCN,#0DEh ; disable software
MOV
WDTCN,#0ADh ; watchdog timer
SETB
EA
; re-enable interrupts
The writes of 0xDE and 0xAD must occur within 4 clock cycles of each other, or the disable operation is ignored.
Interrupts should be disabled during this procedure to avoid delay between the two writes.
Disable WDT Lockout
Writing 0xFF to WDTCN locks out the disable feature. Once locked out, the disable operation is ignored until the
next system reset. Writing 0xFF does not enable or reset the watchdog timer. Applications always intending to use
the watchdog should write 0xFF to WDTCN in their initialization code.
Setting WDT Interval
WDTCN.[2:0] control the watchdog timeout interval. The interval is given by the following equation:
4
3+WDTCN[2:0] x T
SYSCLK , (where T SYSCLK is the system clock period).
For a 2MHz system clock, this provides an interval range of 0.032msec to 524msec. WDTCN.7 must be a 0 when
setting this interval. Reading WDTCN returns the programmed interval. WDTCN.[2:0] is 111b after a system
reset.
Figure 13.3. WDTCN: Watchdog Timer Control Register
R/W
Reset Value
xxxxx111
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xFF
Bits7-0: WDT Control
Writing 0xA5 both enables and reloads the WDT.
Writing 0xDE followed within 4 clocks by 0xAD disables the WDT.
Writing 0xFF locks out the disable feature.
Bit4:
Watchdog Status Bit (when Read)
Reading the WDTCN.[4] bit indicates the Watchdog Timer Status.
0: WDT is inactive
1: WDT is active
Bits2-0: Watchdog Timeout Interval Bits
The WDTCN.[2:0] bits set the Watchdog Timeout Interval. When writing these bits,
WDTCN.7 must be set to 0.
Rev. 1.7
96
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