Watlow MICRODIN - Manual (Page 12)

2 . 2 Wa t l o w M i c r o D I N
Communications Overview
EIA-485 Network
The MicroDIN uses the EIA-485 (formerly, ТRS-485У) hardware interface to
communicate with three wires in a half-duplex configuration, up to 32 remote
devices with a master unit on a network up to 4,000 feet long using 14-26 gauge
wire.
Modbus Protocol
The MicroDIN uses Modbus ª RTU protocol to read and write to registers that
can be viewed or changed from a personal computer. Each MicroDIN
ÔparameterÕ has a corresponding Modbus
ª register and access privileges. The
MicroDIN parameter register numbers and the order of priority appear later in
this chapter.
Chapter 5 details all the MicroDIN parameters, and the Appendix
provides information on how to write custom Modbus ª applications
Set Address/Baud Rate
You must configure the communications speed and network address of the
MicroDIN controller with the eight-bit DIP switch on the top of the unit. Set the
controller address with the first six switches and the network speed (9,600 or
19,200 baud) with the eighth switch. Turn to the DIP switch page later in this
chapter.
Serial Data Format
The MicroDIN uses the an 8-N-1 data format; 8 data bits, no parity, 1 stop bit,
and 1 start bit. See the data format table later in this chapter.
Wiring Tasks
In addition to wiring the controllerÕs input, outputs and power connections, you
must also wire the EIA-232-to-EIA-485 converter; connect your computer to the
MicroDIN, and connect the MicroDIN communications daisy chain. See
ÒCommunications WiringÓ in
Chapter 3 for full detail.
Communications Software
Watlow offers a Windows application for MicroDIN, called, ÒWatLink,Ó which
will both set up and run multiple MicroDINs over an EIA-485 network using the
Modbus
ª protocol. Turn to a screen sample at the end of this chapter.
You may also write your own application (see Appendix for more detail), or
purchase any of several available Modbus
ª -capable control software packages.
Communication
Setup