Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 36)

2–7 Understanding DF1 Protocol
Publication 1770Ć6.5.16 - October 1996
Table 2.C
HalfĆduplex Transmission Symbols
Symbol Type Meaning
DLE SOH control symbol
Sender symbol that indicates the start of a master
message.
DLE STX control symbol
Sender symbol that separates the multiĆdrop
header from the data.
DLE ETX
BCC/CRC
control symbol Sender symbol that terminates a message.
DLE ACK control symbol
Response symbol which signals that a message
has been successfully received.
DLE NAK control symbol
Global link reset command only issued by the
master. Causes the slaves to cancel all messages
that are ready to transmit to the master. Typically,
the slave returns the message and an error code to
the originator.
DLE ENQ control symbol
Sender symbol, issued only by the master, that
starts a poll command.
DLE EOT
BCC
control symbol
Response symbol used by slaves as a response to
a poll when they have no messages to send.
STN data symbol
Station number of the slave node on your
halfĆduplex link.
APP DATA data symbol
Single characters having values 00Ć0F and 11ĆFF.
Includes data from application layer including user
programs and common application routines. A data
10
16
is sent as 10 10 (DLE DLE).
DLE DLE data symbol
Represents the data value or STN value
of 10
16
. See APP DATA.