BB2-7030 User Guide – Rev. 1.0
Page 30
9.
Configuring
the
BB2
7030
01
as
a
Modbus
TCP
Client
The BB2-7030-01 can be a Modbus client or server. As a client (master) you can read Modbus
data from, or write Modbus data to, other Modbus servers (slaves). The BB2-7030 will
periodically poll the other Modbus devices according to register maps you set up. The Modbus
server (slave) devices that you will read/write are defined on the Devices page. To read from a
remote Modbus device, configure a Read Map. To write to a remote Modbus device, configure
Write Map.
Data read from a remote device is stored in a local data object when received. Data written to a
remote device is taken from a local data object when sent. The local data objects are the same
collection of objects that are accessible to other clients via the server map, and accessible to
other BACnet devices via MS/TP or BACnet IP.
The Modbus Devices page is illustrated above. Device number simply shows you where you are
on the device list. Click "next" and "prev" to scroll through the list.
Remote Modbus/TCP devices to be accessed by this device are specified here. Enter the
IP address of the remote device, a name to reference in other pages, a unit number, poll rate, and
check "swapped" if appropriate. Then click "update".
If your slave/server device only supports function codes 5 and 6 for writing, check the Use FC
5/6 box. The default function codes are 15 and 16, which are most widely used.
The term "swapped" only applies to double or float formats. Modbus registers are, by definition,
16 bits of data per register. Access to 32-bit data, either 32-bit integer ("double"), or IEEE 754
floating point ("float"), is supported by the use of two consecutive registers. Modbus protocol is
inherently "big endian", therefore, Modbus by the Module defaults to having the high order
