Intelligent Technologies Modbus to QCPort Adapter Manual
January 2006
MN05002002E (C)
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Page 14
Connect to Modbus
There are two communication connections for the Modbus Adapter, they are Ethernet
and the RS485. The Ethernet connection is 10 Base T and the RS485 connection is a
DB9.
Ethernet
The Ethernet port is a RJ45 10 Base T connection and communicates at 10Mb/s. By
default the speed is 10Mb/s and the mode is set to half duplex. It is possible to change
the duplex mode to full duplex by setting register 7557 to a (1) from (0). For switches that
support full duplex it is recommended to set this register to (1). Refer to Appendix C
register 7557 in the Auto Configuration (AC) Pushbutton Functionality table. It is
suggested that Cat5 or better cable be used; shielded cable is not required but is
suggested if the shields can be tied to ground at one central location.
Notice
If possible, it is advised to run in full duplex mode to eliminate collisions on the
Ethernet network.
Figure 1 Ethernet Cabling
When a hub or a switch is used, the type of cable to use is a straight through cable since
most hubs and switches perform the crossover inside the device. When connecting from
a PC directly to the D77D-EMA, a crossover cable will be needed unless your PC can
automatically detect that a crossover is needed.
Ethernet Server Connections
The Modbus Adapter supports 10 active server connections over port 502. Each of the
server connections can be used to read and write to any of the supported registers within
the Modbus Adapter. It is not required to choose the server connection to communicate
with the Adapter, the Adapter will automatically choose the next available when another
connection is made. For example multiple devices such as a HMI, system controller and
a tool can all be connected to adapter each using a unique connection.
To support the pass-through feature from Ethernet to QCPort Channel A and Channel B,
ports 2000 and 2001 each support 1 active server connection. For more information on
Pass-Through, refer to section Modbus Pass-Through.
Straight Through Cable
Crossover Cable
RJ-45 PIN
RJ-45 PIN
RJ-45 PIN
RJ-45 PIN
1 Tx+
1 Tx+
1 Rx+
3 Tx+
2 Tx-
2 Tx-
2 Rc-
6 Tx-
3 Rc+
3 Rc+
3 Tx+
1 Rc+
6 Rc-
6 Rc-
6 Tx-
2 Rc-
