Rockwell Automation AutoMax ControlNet Communication Interface Module - Manual (Page 72)

Page 72 AutoMax ControlNet Module
Publication number DSMBCN-UM001B-EN-P February 2003
Using the Host Watchdog
The host watchdog is a feature you can use to ensure that the MBCN
stops if the host application stops running. When you enable the host
watchdog, the host AutoMax must check in with the MBCN more
frequently than the watchdog period.
To enable the host watchdog, write the watchdog time in milliseconds to
register 9474, WdTime. The watchdog time can range from 1 to 65534,
corresponding to times of 1 ms to 65.534 seconds.
The host application must then set register 9475, WdFeed, to a non-zero
value within the watchdog period. Every millisecond, the MBCN checks
register 9475. If it is non-zero, the MBCN clears it to 0 and restarts its
internal timer. If it is 0, the MBCN increments its internal timer. If the
internal timer ever reaches the watchdog time, the watchdog times out,
and:
• the NAM state (register 9473) goes to offline
• the keeper state (register 9476) goes to offline
• the module state (register 9472) goes to error
• the scanner global status (register 15745) gets set to bad
• the status of all scanner blocks gets set to D0 01
• the MBCN indicates fatal error 39h on the 7-segment LED
You can enable the host watchdog at any time. Once you have enabled
the host watchdog, you cannot disable it except by cycling power to the
MBCN. You cannot change the watchdog time once it has been set.