User manual

IEC61131 User and Reference Manual
April 22, 2008
576
TeleBUS DF1 Protocol Overview
TeleBUS communication protocols provide a standard communication interface to the
controller. The protocols operate on a wide variety of serial data links. These include RS-232
serial ports, RS-485 serial ports, radios, leased line modems, and dial up modems. The
protocols are generally independent of the communication parameters of the link, with a few
exceptions.
TeleBUS protocol commands may be directed to a specific device, identified by its station
number, or broadcast to all devices. Up to 255 devices may connect to one communication
network.
The TeleBUS protocols provide full access to the I/O database in the controller. The I/O
database contains user-assigned registers and general purpose registers. Assigned
registers map directly to the I/O hardware or system parameter in the controller. General
purpose registers can be used by ladder logic and C application programs to store
processed information, and to receive information from a remote device.
Application programs can initiate communication with remote devices. A multiple port
controller can be a data concentrator for remote devices, by polling remote devices on one
port and responding as a slave on another port.
The protocol type, communication parameters and station address are configured separately
for each serial port on a controller. One controller can appear as different stations on
different communication networks. The port configuration can be set from an application
program, from the TelePACE programming software, or from another Modbus or DF1
compatible device.
Compatibility
There are four TeleBUS DF1 protocols:
 The TeleBUS DF1 Full-Duplex BCC protocol is compatible with the DF1 Full-Duplex data
link layer protocol with block check character (BCC) error checking.
 The TeleBUS DF1 Full-Duplex CRC protocol is compatible with the DF1 Full-Duplex data
link layer protocol with 16-bit cyclic redundancy check (CRC-16) error checking.
 The TeleBUS DF1 Half-Duplex BCC protocol is compatible with the DF1 Half-Duplex data
link layer protocol with block check character (BCC) error checking.
 The TeleBUS DF1 Half-Duplex CRC protocol is compatible with the DF1 Half-Duplex data
link layer protocol with 16-bit cyclic redundancy check (CRC-16) error checking.
Compatibility refers to communication only. The protocol defines communication aspects
such as commands, syntax, message framing, error handling and addressing. The
controllers do not mimic the internal functioning of any programmable controller. Device
specific functions – those that relate to the hardware or programming of a specific
programmable controller – are not implemented.
Serial Port Configuration
Communication Parameters
The TeleBUS DF1 protocols are, in general, independent of the serial communication
parameters. The baud rate and parity may be chosen to suit the host computer and the
characteristics of the data link.
The port configuration can be set in four ways: