VLT
®
FCD Series
Programming, FCD
300
570 Modbus parity and message framing
(M.BUS PAR./FRAME)
Value:
(EVEN/1 STOPBIT)
[0]
(ODD/1 STOPBIT)
[1]
✭
(NO PARITY/1 STOPBIT)
[2]
(NO PARITY/2 STOPBIT)
[3]
Function:
This parameter sets up the drive
’
s Modbus RTU
interface to communicate properly with the master
controller. The parity (EVEN, ODD, or NO PARITY) must
be set to match the setting of the master controller.
Description of choice:
Select the parity that matches the setting for the
Modbus master controller. Even or odd parity is
sometimes used to allow a transmitted word to be
checked for errors. Because Modbus RTU uses
the more efficient CRC (Cyclic Redundancy Check)
method of checking for errors, parity checking is
seldom used in Modbus RTU networks.
571
Modbus communications timeout
(M.BUS COM.TIME.)
Value:
10 ms - 2000 ms
✭
100 ms
Function:
This parameter determines the maximum amount
of time that the drive
’
s Modbus RTU will wait
between characters that are sent by the master
controller. When this amount of time expires, the
drive
’
s Modbus RTU interface will assume that it
has received the entire message.
Description of choice:
Generally, the value of 100 ms is sufficient for Modbus
RTU networks, although some Modbus RTU networks
may operate on a timeout value as short as 35 ms.
If this value is set too short, the drive
’
s Modbus RTU
interface may miss a part of the message. Since the
CRC check will not be valid, the drive will ignore the
message. The resulting retransmissions of messages
will slow communications on the network.
If this value is set too long, the drive will wait longer
than necessary to determine that the message is
completed. This will delay the drive
’
s response to the
message and possibly cause the master controller to
time out. The resulting retransmissions of messages
will slow communications on the network.
✭
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.04.B7.02 - VLT is a registered Danfoss trademark
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