Lenze smd Series Drives - Manual (Page 13)

9 RG-SDMOD
Drive Setup & Operation
4.4 Watchdog Timer
The smd drive is equipped with a Serial Link “Watchdog Timer”. If the Modbus Master wishes to control
the drive (start, stop, forward, reverse, etc.) it must first “Unlock Controls” (section 4.4). If the Watchdog
Timer is enabled and controls have been unlocked, the Master MUST PERIODICALLY COMMUNICATE with
the drive or the timer will timeout. Communications should typically be done at less than 1/2 the interval
specified in n23, Serial Fault Time.
The Watchdog Timer does not operate unless Controls have been UNLOCKED via Register #48, or parameters
writing has been unlocked via Register #49. In case of unlocking parameters only, watchdog timer will
disable write permission but will not stop the drive.
The Watchdog Timer is setup using parameters n22 (Serial Timeout Action) and n23 (Serial Fault Time).
Selection of n22 determines the smd drive's reaction to serial timeout:
n22 = 0: Not Active The Watchdog Timer is disabled
n22 = 1: Controller Inhibit If the drive doesn't receive valid communication for period longer
than time specified in parameter n23, it will COAST to a STOP and
status display (c61) will show inhibit state 'Inh'.
n22 = 2: Quick Stop If drive doesn't receive valid communication for period longer than
time specified in parameter n23, it will RAMP to a STOP and status
display (c61) will show inhibit state 'Stp'.
n22 = 3: Trip Fault FC3 If drive doesn't receive valid communication for period longer than
time specified in parameter n23, it will TRIP with an 'FC3' fault.
The setting of Parameter n23, Serial Fault Time, sets the serial timeout length in miiliseconds. The valid
range is 50 - 65535 ms and the default setting is 50ms.
NOTE - Trip Prevention
To prevent erroneous timeout trips, make sure the time set in parameter n23 is appropriate
for the particular network. The defualt value of 50ms may be too restrictive.
WARNING
Disabling the Watchdog Timer may cause injury to personnel and/or damage to equipment.
The Watchdog Timer should only be disabled during configuration or diagnosis to prevent
nuisance timeout trips.