User manual

Page 57 February 2010
digital output at B. Local Register 4320 specifies the register for the onboard digital output at B
(since B is the local unit at which the mapping is configured). I/O Count 1 specifies that only one
I/O point is being transferred (i.e. the single digital I/O). Function Code 02: Read Discretes specifies
the standard ModBus function code to read discrete (i.e. digital) inputs. Destination Register 4300
specifies the register for the onboard digital input at unit C (since C is the destination unit for this
mapping). Device ID 1is the ID of the onboard ModBus TCP Server at C. Server IP Address
192.168.0.200 is the IP address of unit C – which is the ModBus TCP Server we are reading from.
Response Timeout 1000 ms specifies that unit C must respond to this message within 1000ms.
Comm Fail Register 0 specifies the local register where the communications status for this mapping
will be stored.
The second mapping reads 8 registers from serial unit D into onboard registers in unit B. Note that
in this case the specified Device ID 6 is the ModBus Address of the serial device D, while the
Server IP Address 192.168.0.200 is the IP Address of unit C since the ModBus TCP to RTU
Gateway at unit C converts the ModBus TCP message to ModBus RTU and routes it out the serial
port to unit D.
The third mapping takes the 8 registers read by the second mapping and writes them to the serial
unit A. The specified Device ID 5 is the ModBus Address of the serial device A, and the Server IP
Address 192.168.0.196 is the IP Address of the local unit B since the local ModBus TCP to RTU
Gateway is to route the message out the serial port to unit A.
Since the WI-MOD-E supports ModBus TCP Client and Server simultaneously, the ModBus TCP
Server for unit B above could also be enabled. This would allow one (or more) external ModBus
TCP Clients anywhere on the extended wired or wireless network to connect to unit B and monitor