Pulsafeeder Pulsar DLCM - Manual (Page 120)

114
14. PulsaNet Specification
For simplicity, the DLC, DLCM, MLC, MLCM, NEMA-4X and NEMA-7 variations will ALL be referred
to as the DLC unless otherwise noted.
14.1 Introduction
The DLC PulsaNet communication system is an implementation of the industry standard MODBUS®
protocol. The physical layer uses an RS-485 four-wire multi-drop scheme. Up to 32 slave units can be
connected to a single master on the same set of wires. They can share those wires with PLC’s and PC’s
that use the same method of communication.
The MODBUS protocol was created in 1978 by Modicon as a simple way for transferring data between
controllers. Since it’s creation it has become a de-facto industry standard used by multiple control and
sensor companies. Today the MODBUS® protocol is the single, most supported protocol amongst
automation devices.
The MODBUS protocol is both a trademark and a fully owned product of Schneider Automation. The
specification is freely distributed on the Schneider Automation home page on the World Wide Web.
With the few noted exceptions in this document, PulsaNet complies with the Schneider MODBUS
protocol specification. If you are interested in developing a MODBUS application to interface with
PulsaNet, please obtain the MODBUS specification from the Schneider Automation web site.
14.2 Operational Overview
The DLC has several different methods of operation when it comes to Serial Communications and
MODBUS Mode.
1. A PC or PLC MASTER can Monitor Information in the DLC while it is in any mode of operation.
2. A PC or PLC MASTER can also WRITE certain information when the DLC is in MODBUS MODE.
3. A DLC MASTER can control up to 32 DLC SLAVES in a similar way that Analog signals can be used
to daisy chain units together. Additional features that are available are:
b) The DLC SLAVE can follow the on/off motor state of the master and,
c) The DLCM SLAVE can follow the STROKE and SPEED separately of a DLCM MASTER.
4. A DLC MULTIPLEX MASTER can control MULTIPLEX slaves permitting better integration of the
‘motor-less’ DLC’s.