Rockwell Automation 1762-Lxxxx MicroLogix 1200 Programmable Controllers - Manual (Page 135)

Publication 1762-UM001G-EN-P - March 2011
Connect to Networks via RS-232 Interface E-5
DH-485 Communication
Protocol The DH-485 protocol defines the communication between multiple devices
that coexist on a single pair of wires. DH-485 protocol uses RS-485
Half-duplex as its physical interface. (RS-485 is a definition of electrical
characteristics; it is not a protocol.) RS-485 uses devices that are capable of
co-existing on a common data circuit, thus allowing data to be easily shared
between devices.
The DH-485 protocol supports two classes of devices: initiators and
responders. All initiators on the network get a chance to initiate message
transfers. To determine which initiator has the right to transmit, a token
passing algorithm is used.
Devices that use the DH-485 Network
In addition to the MicroLogix 1200 controllers, the devices shown in the
following table also support the DH-485 network.
Table E.1 Allen-Bradley Devices that Support DH-485 Communication
Catalog
Number Description Installation Function Publication
Bulletin 1761
Controllers MicroLogix 1000 Series C or
higher These controllers support DH-485 communications. 1761-6.3
Bulletin 1764 MicroLogix 1500 Series A or
higher These controllers support DH-485 communications. 1764-UM001
Bulletin 1747
Processors SLC 500
Processors SLC Chassis These processors support a variety of I/O requirements and
functionality.
1747-UM011
1746-BAS BASIC Module SLC Chassis Provides an interface for SLC 500 devices to foreign devices.
Program in BASIC to interface the 3 channels (2 RS232 and 1
DH-485) to printers, modems, or the DH-485 network for data
collection.
1746-UM004
1746-PM001
1746-RM001
1785-KA5 DH
+
/DH-485
Gateway
(1771) PLC
Chassis Provides communication between stations on the PLC-5 (DH+)
and SLC 500 (DH-485) networks. Enables communication and
data transfer from PLC to SLC 500 on DH-485 network. Also
enables programming software programming or data acquisition
across DH+ to DH-485. 1785-6.5.5
1785-1.21
2760-RB Flexible Interface
Module (1771) PLC
Chassis Provides an interface for SLC 500 (using protocol cartridge
2760-SFC3) to other A-B PLCs and devices. Three configurable
channels are available to interface with Bar Code, Vision, RF,
Dataliner, and PLC systems. 1747-6.12
2760-ND001
1784-KTX,
-KTXD PC DH-485 IM IBM XT/AT
Computer
Bus Provides DH-485 using RSLinx. 1784-6.5.22
1784-PCMK PCMCIA IM PCMCIA slot
in computer
and
Interchange Provides DH-485 using RSLinx. 1784-6.5.19
1747-PT1 Hand-Held
Terminal NA Provides hand-held programming, monitoring, configuring, and
troubleshooting capabilities for SLC 500 processors. 1747-NP002