Rockwell Automation 1766-Lxxxx MicroLogix 1400 Programmable Controllers User Manual - Manual (Page 224)

184 Rockwell Automation Publication 1766-UM001H-EN-P - May 2014
Appendix E Connecting to Networks via RS-232/RS-485 Interface
The MicroLogix controller supports the DF1 Full-Duplex protocol via RS-232
connection to external devices, such as computers, or other controllers that
support DF1 Full-Duplex.
DF1 is an open protocol. Refer to DF1 Protocol and Command Set Reference
Manual, publication 1770-6.5.16, for more information.
DF1 Full-Duplex protocol (also referred to as DF1 point-to-point protocol) is
useful where RS-232 point-to-point communication is required. DF1 protocol
controls message flow, detects and signals errors, and retries if errors are detected.
Example DF1 Full-Duplex Connections
For information about required network connecting equipment, see Chapter 4 ,
Communication Connections .
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-232/485 port on the MicroLogix as both a Half-Duplex
programming port and a Half-Duplex peer-to-peer messaging port.
DF1 Half-Duplex Operation
A DF1 Half-Duplex master device initiates all communication by “polling” each
slave device. The slave device may only transmit when it is polled by the master. It
Personal Computer
CH0
MicroLogix 1400
MicroLogix 1400
1761-CBL-PM02
Personal
Computer
Modem cable
Modem
Modem 1761-CBL-PM02
Null modem
adapter
CH0
44608