Advantech PCE-7214, User Manual

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PCE-7214 User Manual 58
A.1 Watchdog Timer
The PCE-7214's watchdog timer can be used to monitor system software operation
and take corrective action if the software fails to function after the programmed
period. This section describes the operation of the watchdog timer and how to pro-
gram it.
A.1.1 Watchdog timer overview
The watchdog timer is built into the super I/O controller W83627UHG. It provides the
following functions for user programming:
 Can be enabled and disabled by user's program.
 Timer can be set from 1 to 255 seconds or 1 to 255 minutes.
 Generates an interrupt or resets signal if the software fails to reset the timer
after time-out.
A.1.2 Reset/ Interrupt selection
The JWDT1 jumper is used to select reset in the event the watchdog timer is tripped.
See Chapter 1 for detailed jumper settings.
A.1.3 Programming the Watchdog Timer
The I/O port address of the watchdog timer is 2E(hex) and 2F(hex).
2E (hex) is the address port. 2F(hex) is the data port.
You must first assign the address of register by writing address value into address
port 2E(hex), then write/read data to/from the assigned register through data port 2F
(hex).
Note! The interrupt output of the watchdog timer is a low level signal. It will be
held low until the watchdog timer is reset.