Perle Systems IOLAN SCS - Manual (Page 322)

Configuring Modbus
322 IOLAN Device Server User’s Guide, Version 3.6
Modbus Gateway Settings
The scenarios in this section are used to illustrate how the IOLAN’s Modbus Gateway settings are
incorporated into a Modbus device environment. Depending on how your Modbus Master or Slave
devices are distributed, the IOLAN can act as both a Slave and Master Gateway(s) on a multiport
IOLAN or as either a Slave or Master Gateway on a single port IOLAN.
Modbus Master Gateway
The IOLAN acts as a Master Gateway when the Modbus Master is connected to a serial port on the
IOLAN. Each Modbus Master can communicate to UIDs 1-247.
Modbus Slave Gateway
The IOLAN acts as a Slave Gateway when the Modbus Master resides on the TCP/Ethernet network
and the Modbus Slaves are connected to the serial ports on the IOLAN. Note: The IOLAN provides a
single gateway to the network-attached Modbus Masters. This means that all Modbus Slaves attached
to the IOLAN’s serial ports must have a unique UID. Multiple Masters on the network can
communicate with these Modbus Slaves. Note: If a transaction is in progress to a Modbus Slave,
other requests to that same device will be queued until that transaction is complete.
IOLAN
Network
EIA-232
EIA-422/485
TCP
Modbus Slave
Modbus Slave
Modbus Slave
Modbus Master
Master Gateway
Modbus Master
Serial
IOLAN
Network
EIA-232
EIA-422/485
TCP
Modbus Slave
Modbus Slave
Modbus Slave Modbus Master
Slave Gateway
Modbus Master
Modbus Slave
Serial