ADLINK Technology PCI-8254, Руководство пользователя, Страница: 211 / 226

Motion Control Theory 197
PCI-8254 / PCI-8258
4.11.2.3 Watch Dog
The watchdog protection mechanism is a timer inside the
controller. Timeout of the timer will enable predefined response
actions including Servo off, turning off digital output and turning off
PWM output. After the watchdog protection mechanism is
enabled, the user program must be in responsible status. Before
timeout of the timer, the watchdog mechanism should be reset
continuously to restart timing of the timer. As long as the user
program remain in responsible status relevant events shall not be
triggered. In another words, the watchdog protection mechanism
is used to detect stagnation (failure) status of the upper control
program. If stagnation situation is encountered, the controller
triggers a protection mechanism to close signal output.
You may use interrupt function in Windows environment as
described below:
1. Set up trigger event of timer timeout
2. Enable watchdog protection mechanism
3. Reset timer within cycle time
See below for relevant APS APIs:
APS_wdt_set_action_event ();
APS_wdt_set_action_event ();
APS_wdt_start ();
APS_wdt_get_timeout_period ();
APS_wdt_reset_counter ();
Detailed operation methods are described below:
1. Set up trigger event of timer timeout:
Use APS_wdt_set_action_event () function to set up
trigger event.
Use
APS_wdt_get_action_event () function to get trigger
event.
2. Enable watchdog protection mechanism:
Use APS_wdt_start () to set up a timeout period and
enable the watchdog function then the internal timer starts
clicking. Set timeout period to "0" to disable watchdog
function.
Use
APS_wdt_get_timeout_period () to read in the
timeout settings.