Allen-Bradley MicroLogix 1200 - Communication Protocol; Devices that Use the DH-485 Network

Publication 1762-UM001D-EN-P - March 2004
Connecting 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+
TM
/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