Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 352)

Publication AG-UM008C-EN-P - February 2005
B-6 Basic DF1 Protocol Troubleshooting
DF1 Full-Duplex Protocol To help you diagnose communication problems, you can use a serial
line analyzer to see the data packets being transmitted on the RS-232
link between the DTE and the DCE. For further details, see the DF1
Protocol and Command Set Reference Manual, publication
1770-RM516.
Table B.3 Summary DF1 Full-Duplex Protocol Packet Exchanges
Table B.4 Identify the DF1 Full-Duplex Packets
See ANSI X3.4, CCITT V.3, or ISO 646 for the standard definition of
these characters.
For the See
different types of communication packet
exchanges between two full-duplex stations Table B.3
definitions of the packets Table B.4
Message Type Sender Station’s Packet Receiver Station’s Packet
Sender station transmits a MSG instruction to a receiving
station; receiver station acknowledges DLE STX message DLE ETX BCC/CRC DLE ACK
Sender station transmitting a MSG instruction to a receiver
station; receiver station cannot receive the message or error in
transmission DLE STX message DLE ETX BCC/CRC DLE NAK
Sender station receives a corrupted DLE ACK from the receiver
station; sender station requests re-transmission of last control
symbol; receiver station sends the DLE ACK again DLE ENQ DLE ACK
Symbol Hexadecimal Binary Type Meaning
DLE STX 10 02 0001 0000 0000 0010 control symbol Start of header
Sender symbol that indicates the start of a
message
DLE ETX BCC/CRC 10 03 xx(xx) 0001 0000 0000 0011 control symbol Sender symbol that terminates a message
DLE ENQ 10 05 0001 0000 0000 0101 control symbol Sender symbol that requests retransmission of
a response symbol from the receiver
DLE ACK 10 06 0001 0000 0000 0110 control symbol Response symbol that signals that a message
has been successfully received
DLE DLE 10 10 0001 0000 0001 0000 data symbol Represents the data value of 10 (hex)
DLE NAK 10 15 0001 0000 0001 0101 control symbol Negative acknowledgment
Response symbol that signals that a message
was not received successfully
APP DATA application specific data symbol Single characters having values 00-0F and 11-FF
Includes data from the application layer
including user programs and common
application routines