Technical Instructions
Modbus RTU Interface Module for SED2
Document Number 155-767
February 25, 2009
Page 8
Siemens Industry, Inc.
Watchdog Timer
Setup
To enable an Interface Module Host Watchdog Function, the
Interface Module
Master
controls the first two holding Registers, WDOG TIME (40001) and WDOG ACTION
(40002).
When the Host Watchdog Function activates, the
Interface Module
does not receive any
further communications from the Master for a period of time determined by WDOG
TIME (40001). With WDOG ACTION (40002) set to 1, the SED2 stops on loss of
communications.
To activate the
Interface Module
Host Watchdog Function, set:
•
WDOG TIME (40001) to the amount of time in milliseconds that must pass
with no further
Interface Module
communications.
•
WDOG ACTION (40002) to
1
so that the SED2 stops on loss of
communications with the Modbus master.
To deactivate the
Interface Module
Host Watchdog Function, set WDOG ACTION to
0
.
SED2 Parameter 2014, USS Telegram Off Time, controls a Watchdog timer function for
the USS port.
•
Once the
Interface Module
establishes communications with the SED2, if the
Interface Module
stops communicating with the SED2, the SED2 automatically
enters the fault state with a F0070 fault number.
•
Parameter P2014 specifies the timeout value for the USS Watchdog timer
function.
If P2014 is set to 0, the USS Watchdog timer is disabled. If P2014 is set to a non-zero
value, the USS Watchdog timer function is enabled and the timeout value is the P2014
non-zero value.
If using the USS Watchdog timer function with the Interface Module, set P2014 to a
value of 100 or greater so that accidental faults do not occur because of normal
communications delays between the Interface Module and the SED2.
