ADLINK Technology NuPRO-900A, Руководство пользователя

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Watchdog Timer
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35
5
Watchdog Timer
This chapter explains the operation of the NuPRO-900A’s watchdog timer. It
provides an overview of watchdog operation and features. Sample programs
are located at X:\CHIPDRV\WDT\DOS\NP900
5.1 Watchdog Timer Overview
The primary function of the watchdog timer is to monitor the NuPRO-900A
operation and to reset the system if the software fails to function as
programmed. The major features of the watchdog timer are:
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Enabled and disabled through software control
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Armed and strobed through software control
Figure 8: Watchdog Timer Architecture
The NuPRO-900A custom watchdog timer circuit is implemented in a
programmable logic device. The watchdog timer contains two "Control and
Status Register" (CRF5 and CRF7 of logical device 8).
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The watchdog times out after a selected timeout interval.
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A hard reset occurs.
The timeout period is 1 – 255 seconds or 1 – 255 minutes.
Address/Data
Watchdog Circuit
Reset
Counter Slow Clock
Port 4Eh
Control and
status
Register