Lenze TCF Series Drives Modbus Communications - Manual (Page 12)

RG-TFMOD 8
Drive Setup & Operation
4.6 Watchdog Timer
All AC Tech drives are 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” (refer to section 5.7).
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 5sec intervals as the Watchdog Timer faults at 10 seconds. A Watchdog timeout forces the drive
to stop because it is assumed that the failure of periodic communications with the drive could be a loss
of the serial link with the accompanying loss of ability to command the drive to stop. 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.
Watchdog Timer Controls
− For some applications, it is inappropriate to shut down the drive because of a Watchdog Timeout.
Therefore, we have provided a means of disabling the Watchdog using Programming Parameter
#15 (SERIAL LINK):
Programming Parameter #15 controls both the enabling of the serial link and the Watchdog.
By setting Parameter #15 to one of the selections WITH TIMER enables the serial link WITH the
Watchdog. Conversely, setting Parameter #15 to WITHOUT TIMER enables the serial link WITHOUT
the Watchdog.
− If the Watchdog Timer has been disabled, the Unlock Control Register #48 or Unlock Writing
Register #49 must still be asserted in order to write to Register #1 (Drive Control) or to any of
the programming parameters (in case of unlocking writing). However, there are no longer any
constraints on how often the Master must communicate with the drive.
4.7 Monitoring Only Operation
1. Power up drive in TERMINAL mode with serial enabled.
2. Simply read AC Tech Register #24 (Modbus Register #25) or any other readable register.
3. No unlocking or watchdog issues apply for monitoring.
4.8 Normal Control Operation Sequence
1. Power up drive with serial enabled and TB1 asserted.
2. Unlock control by writing a zero to Register #48.
3. Control drive operation via various commands to Register #1 (Start, Stop, Reverse direction, etc.) and
change the keypad command speed by writing to Register #40.
Note: Drive must be in “MANUAL” (see Register #1 [drive control]) and Parameter #5 (standard speed
source) must be set to 01 (keypad) in order to control speed via Register #40.