Rockwell Automation 5370 CVIM Communications Manual - Manual (Page 96)

Chapter 5
Using the RS–232 Ports
5–26
The remainder of this chapter describes DF1 protocol. After you have made
the equipment connections and configured the CVIM module for RS–232
communications, DF1 packets of data can be sent to the CVIM module.
DF1 is an Allen–Bradley developed software convention used for RS–232
communications. DF1 provides some handshaking and data–packing formats
which allow for fast communications with integrity of the data.
This chapter describes a simple application level of DF1 for communications
between a CVIM module and a computer host. This application level
requires that all transmitted data be preceded by a header and terminated by a
trailer and a Block Check Character (BCC). In addition, ACK / NAK
characters and simple time out conventions are used to ensure the integrity of
the data.
A more complete implementation of DF1 can include layered software for
point-to-point and multidrop links using several layers:
Data Link Layer
Transport Network Layer(s)
Application Layer
We do not provide a complete description of DF1 in this manual. We have
only provided information necessary to transmit data between a host
computer and the CVIM module. If you want to learn more about DF1, we
suggest reading Publication 2802-800 (Line Scan Camera User’s Manual).
Appendix A of this publication provides a thorough description of DF1.
In the DF1 protocol mode, all data is transferred between the CVIM module
and a host as bytes with a value between 00(hex) and FF(hex). Refer to
Appendix E to convert control codes like ACK and NAK to/from
hexadecimal values.
DF1 Protocol
What is DF1?
DF1 Character Set