參數(shù)資料
型號: MR80C52EXXX-25/883
廠商: ATMEL CORP
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 25 MHz, MICROCONTROLLER, CQCC44
封裝: LCC-44
文件頁數(shù): 28/46頁
文件大?。?/td> 4720K
代理商: MR80C52EXXX-25/883
33
ATtiny20 [DATASHEET]
8235E–AVR–03/2013
8.4.2
Code Examples
The following code example shows how to turn off the WDT. The example assumes that interrupts are controlled (e.g., by
disabling interrupts globally) so that no interrupts will occur during execution of these functions.
Note:
8.5
Register Description
8.5.1
WDTCSR – Watchdog Timer Control and Status Register
Bit 7 – WDIF: Watchdog Timer Interrupt Flag
This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is configured for interrupt. WDIF is
cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, WDIF is cleared by
writing a logic one to the flag. When the WDIE is set, the Watchdog Time-out Interrupt is requested.
Bit 6 – WDIE: Watchdog Timer Interrupt Enable
When this bit is written to one, the Watchdog interrupt request is enabled. If WDE is cleared in combination with this
setting, the Watchdog Timer is in Interrupt Mode, and the corresponding interrupt is requested if time-out in the
Watchdog Timer occurs.
If WDE is set, the Watchdog Timer is in Interrupt and System Reset Mode. The first time-out in the Watchdog Timer will
set WDIF. Executing the corresponding interrupt vector will clear WDIE and WDIF automatically by hardware (the
Watchdog goes to System Reset Mode). This is useful for keeping the Watchdog Timer security while using the interrupt.
To stay in Interrupt and System Reset Mode, WDIE must be set after each interrupt. This should however not be done
within the interrupt service routine itself, as this might compromise the safety-function of the Watchdog System Reset
mode. If the interrupt is not executed before the next time-out, a System Reset will be applied.
Assembly Code Example
WDT_off:
wdr
; Clear WDRF in RSTFLR
in
r16, RSTFLR
andi
r16, ~(1<<WDRF)
out
RSTFLR, r16
; Write signature for change enable of protected I/O register
ldi
r16, 0xD8
out
CCP, r16
; Within four instruction cycles, turn off WDT
ldi
r16, (0<<WDE)
out
WDTCSR, r16
ret
Bit
76543210
WDIF
WDIE
WDP3
WDE
WDP2
WDP1
WDP0
WDTCSR
Read/Write
R/W
R
R/W
Initial Value
0000
X
0
00
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