Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 335)

Understanding the Communication Protocols
D–7
Modem
Modem Modem Modem Modem Modem
RS-232
(DF1 Protocol)
MicroLogix 1000
Programmable
Controller (Series D) SLC 5/03 Processor
Modular Controller
Rockwell Software WINtelligent LINX, RSLinx 2.0 (or higher),
SLC 5/03, SLC 5/04 and SLC 5/05, or PLC-5 processors
configured for DF1 Half-Duplex Master
MicroLogix 1000
Programmable
Controller (Series D) MicroLogix 1000
Programmable
Controller (Series D) SLC 500 t
Fixed I/O Controller
with 1747-KE
Interface Module
Considerations When Communicating as a DF1 Slave on a Multi-drop Link
When communication is between either your programming software and a
MicroLogix 1000 Programmable Controller or between two MicroLogix
Programmable Controllers via a slave-to-slave connection on a larger multi-drop
link, the devices depend on a DF1 Master to give each of them polling permission to
transmit in a timely manner. As the number of slaves increases on the link (up to
254), the time between when your programming software or the MicroLogix
Controller is polled also increases. This increase in time may become larger if you
are using low baud rates.
As these time periods grow, the following values may need to be changed to avoid
loss of communication:
•
programming software - increase poll timeout and reply timeout values
•
MicroLogix Programmable Controller - increase poll timeout