West Control Solutions N6600 - Manual (Page 37)

4 MODBUS RTU COMMUNICATIONS
The Plastics Controller may be equipped with two-wire RS485-compatible serial
communications, by which means communication may occur between the
Controller and a master device (e.g. a computer or terminal).
4.1 COMMUNICATIONS WRITE ENABLE/DISABLE
When Communications Write operations are enabled (in Set Up Mode - see
Subsection 3.2.39), the Controller parameters may be adjusted by the master
device via the serial communications link. If communications Writes are disabled,
the Controller will not adjust or change any parameters in response to commands
received from the master device and will send a negative acknowledgement in
response to such commands. Whether communications Writes are enabled or
disabled, the Controller will return the requested information in response to
interrogation from the master device.
4.2 PHYSICAL REQUIREMENTS
4.2.1 Character Transmission
The data format is fixed to be one start bit, eight data bits and one stop bit. The
Baud rate may be selected to be 1200, 2400, 4800 (default) or 9600 Baud. The
parity is selectable to be even, odd, or none.
4.2.2 Line Turn-round
The line turn-round timings adhere to the industry standard.
4.3 MODBUS RTU PROTOCOL
The standard RS485 Communications Option and the Enhanced RS485
Communications option both use the industry standard MODBUS protocol. The
following restrictions are imposed:
• Baud rates may be set to 1200, 2400, 4800 or 9600 Baud only.
• Support for multi-parameter Write operations is limited to support of the
Multi-Word Write Function (Number 16) but permits writing of one
parameter only per message.
• The multi-parameter Read operations support a maximum of 10
parameters per message.
The following MODBUS functions are supported (JBUS names, where applicable,
are given in italics):
O075-4 4-1
PM-0075