Allen-Bradley MicroLogix 1200 - DF1 Half-Duplex Protocol

Publication 1762-UM001D-EN-P - March 2004
E-2 Connecting to Networks via RS-232 Interface
Example DF1 Full-Duplex Connections
For information about required network connecting equipment, see
Chapter 4, Communication Connections.
We recommend using an AIC+, catalog number 1761-NET-AIC, as
your optical isolator.
DF1 Half-Duplex Protocol
DF1 Half-Duplex protocol is a multi-drop single master/multiple slave
network. DF1 Half-Duplex protocol supports data transparency
(American National Standards Institute ANSI - X3.28-1976 specification
subcategory D1). In contrast to DF1 Full-Duplex, communication
takes place in one direction at a time. You can use the RS-232 port on
the MicroLogix 1200 as both a Half-Duplex programming port and a
Half-Duplex peer-to-peer messaging port.
MicroLogix 1200 can act as the master or as a slave on a Half-Duplex
network. When the MicroLogix 1200 is a slave device, a master device
is required to "run" the network. Several other Allen-Bradley products
support DF1 Half-Duplex master protocol. They include the SLC
5/03™ and higher processors, enhanced PLC-5
®
processors and
Rockwell Software RSLinx (version 2.x and higher).
DF1 Half-Duplex supports up to 255 devices (address 0 to 254) with
address 255 reserved for master broadcasts. As a DF1 Half-Duplex
slave device, the MicroLogix 1200 supports broadcast reception. As a
DF1 Half-Duplex master, the MicroLogix 1200 supports both the
reception and initiation of broadcast write commands (via the MSG
instruction). The MicroLogix 1200 also supports Half-Duplex modems
using RTS/CTS hardware handshaking.
TERM
A
B
COM
SHLD
CHS GND
TX
TX PWR
TX
DC SOURCE
CABLE
EXTERNAL
TERM
A
B
COM
SHLD
CHS GND
TX
TX PWR
TX
DC SOURCE
CABLE
EXTERNAL
Personal Computer
Modem cable
Modem
Modem
Optical Isolator
1761-CBL-PM02
MicroLogix 1200
Personal Computer
MicroLogix 1200
Optical
Isolator
1761-CBL-PM02
1761-CBL-AM00 or 1761-CBL-HM02