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The above example demonstrates how a Modbus/TCP Client (Master) can connect to
one or more Modbus RTU (i.e serial) Slaves. In this example the RM-90 Access Point is
configured with the “RS-232 Modbus/TCP to RTU Gateway” enabled. Once enabled, the
gateway converts the Modbus/TCP queries received from the Master into Modbus RTU
queries and forwards these over the RS-232 port to the Slave. When the serial response
to the query arrives from the Slave, it is converted to a Modbus/TCP response and for-
warded via the network to the Modbus/TCP Master. If no response was received serially
by the RM-90 within the configured Response Timeout, the RM-90 will initiate a number
of retries specified by the configured Maximum Request Retries.
The Modbus TCP to RTU Server may be configured to operate on either the RS-232 or
RS-485 port. It does not support operation on both ports at the same time.
Enable RS-232 Modbus TCP to
RTU Gateway
Check this box to enable the Modbus TCP to
RTU Server on the RS-232 port. Only a single
serial port is allowed at a time.
Enable RS-485 Modbus TCP to
RTU Gateway
Check this box to enable the Modbus TCP to
RTU Server on the RS-485 port. Only a single
serial port is allowed at a time.
Data Rate
The serial data rate desired. Serial data rates
available range from 110bps to a maximum of
38,400 bps.
Data Bits Parity Stop Bits
The data format desired. Data formats of 8N1,
7E1, 7O1, 7E2, 7O2 are supported.
Pause Between Requests
Enter the delay between serial request retries in
milliseconds.
Response Timeout
Enter the serial response timeout in milliseconds
– a serial retry will be sent if a response is not
received within this timeout.
Connection Timeout
Enter the TCP connection timeout in seconds – if
no Modbus/TCP data is received within this time-
out then the TCP connection will be dropped.
Set this field to zero for no timeout.
Maximum Request Retries
Enter the maximum number of request retries
performed serially.
Maximum Connections
Enter the maximum number of simultaneous TCP
connections to the server allowed.
3.13 Digital Input/Output
Presently the only function for the Digital I/O channel is to provide a status output of the
module communications. If the RM-90 disassociates from another unit (that is, there is no
wireless link), you can configure the digital output to turn ON or OFF.
