Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 152)

Publication 1785-UM012D-EN-P - July 2005
10-2 Communicating with Devices on a Serial Link
Configuring the Controller
Serial Port Channel 0 is the serial port and is configurable for RS-232C, RS-423, or
RS-422A compatible communication. Use switch assembly SW2 to specify the
serial port configuration.
To set the controller switch, see chapter 23 or look on the side label of the
controller, which shows the switches in switch assembly SW2 and a table
listing the settings.
Using Channel 0 You can use the controller’s serial port (channel 0) to connect the controller to
devices that:
• can send and receive ASCII characters by using User mode (ASCII
communication)
• communicate using DF1 protocol by using one of three available System
modes
User Mode
In user mode, all data are received and sent via a buffer. To access or send this
data, use ASCII instructions in your ladder program. The ASCII data a PLC-5
controller sends contain no additional protocol characters.
In user mode, only ASCII instructions can be used. If you try to use a message
(MSG) instruction that references the serial port, the error (.ER) bit is set.
Examples of ASCII peripheral devices are:
• ASCII terminals
• Bar code readers
• Allen-Bradley Dataliners
• Weigh scales
• Printers
System Mode
In system mode, the controller interprets a command from another device.
Use system mode when you need to communicate with other devices on a link.
System mode, with DF1 protocol, is a separate and unique communication
link from the DH+ link.