Operating instructions

VLT

2800, VLT

6000 HVAC and VLT

8000 AQUA Modbus RTU

Modbus RTU

Programming

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’sModbusRTUwillwait

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 time-out value as short as 35 ms.

If this value is set too short, the drive’sModbusRTU

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.10.S2.02 - VLT is a registered Danfoss trademark