参数资料
型号: ST92186B3BK
厂商: STMICROELECTRONICS
元件分类: 微控制器/微处理器
英文描述: 16-BIT, MROM, 24 MHz, MICROCONTROLLER, PDIP32
封装: PLASTIC, SDIP-32
文件页数: 117/148页
文件大小: 1664K
代理商: ST92186B3BK
Obsolete
Product(s)
- Obsolete
Product(s)
Obsolete
Product(s)
- Obsolete
Product(s)
70/148
ST92186B - TIMER/WATCHDOG (WDT)
TIMER/WATCHDOG (Cont’d)
7.1.3.2 Preventing Watchdog System Reset
In order to prevent a system reset, the sequence
AAh, 55h must be written to WDTLR (Watchdog
Timer Low Register). Once 55h has been written,
the Timer reloads the constant and counting re-
starts from the preset value.
To reload the counter, the two writing operations
must be performed sequentially without inserting
other instructions that modify the value of the
WDTLR register between the writing operations.
The maximum allowed time between two reloads
of the counter depends on the Watchdog timeout
period.
7.1.3.3 Non-Stop Operation
In Watchdog Mode, a Halt instruction is regarded
as illegal. Execution of the Halt instruction stops
further execution by the CPU and interrupt ac-
knowledgment, but does not stop INTCLK, CPU-
CLK or the Watchdog Timer, which will cause a
System Reset when the End of Count condition is
reached. Furthermore, ST_SP and S_C bits are
ignored. Hence, regardless of their status, the
counter always runs in Continuous Mode, driven
by the internal clock.
Figure 40. Watchdog Timer Mode
TIMER START COUNTING
WRITE WDTRH,WDTRL
WD EN=0
WRITE AAh,55h
INTO WDTRL
RESET
SOFTWARE FAIL
(E.G. INFINITE LOOP)
OR PERIPHERAL FAIL
VA00220
PRODUCE
COUNT RELOAD
VALUE
COUNT
G
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