3. MODBUS Protocol
(Available on 2493 models only)
IM 249x-COMM
8
Modbus is an open communications protocol developed by Modicon Inc. to
connect controllers and other devices over a network. It defines a standard way
of passing messages between devices so that they will be able to parse an
incoming message and take any appropriate action necessary.
Devices communicate using a master-slave technique, in which only one device
(the master) can initiate transactions (called ‘queries’). The other devices (the
slaves) respond by supplying the requested data to the master, or by taking the
action requested in the query. The master can address individual slaves, or can
initiate a broadcast message to all slaves. Slaves return a message (called a
‘response’) to queries that are addressed to them individually. Responses are
not returned to broadcast queries.
The Power Series
Plus
always acts as a slave in accordance with The Modicon
Modbus Reference Guide PI-MBUS-300. It has the following characteristics:
Interface:
RS-485
Transmission modes:
ASCII (7 data bits) or RTU (8 data bits). Both use 2
stop bits
Parity:
even, odd, or no parity
Baud Rate:
9600, 4800, 2400 or 1200 bps
The default settings from the factory are RTU mode, no parity, 9600 bps.
The following function codes are supported:
03 – Read Holding Registers
04 – Read Input Registers
The device will respond to either of these codes in the exact same way. They
were both included to allow compatibility with a wider range of systems. You can
read any single register or the following sets of registers:
1 thru 14 - all the settings, except output ranges
22 thru 36 - all the output range settings
37 thru 50, 67 thru 80, 97 thru 110 – Latest, Minimums and Maximums for
Volts, Amps and Frequency
51 thru 56, 81 thru 86, 111 thru 116 – Latest, Minimums and Maximums
for Watts, VARs, and Power Factor
