Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 35)

2–6 Understanding DF1 Protocol
Publication 1770Ć6.5.16 - October 1996
Both half-duplex and full-duplex protocols are character-oriented.
They use the ASCII control characters in the tables below, extended
to eight bits by adding a zero for bit 7:
Table 2.A
HalfĆduplex Protocol
Abbreviation Hexadecimal Value Binary Value
STX 02 0000 0010
SOH 01 0000 0001
ETX 03 0000 0011
EOT 04 0000 0100
ENQ 05 0000 0101
ACK 06 0000 0110
DLE 10 0001 0000
NAK 0F 0000 1111
Table 2.B
FullĆduplex Protocol
Abbreviation Hexadecimal Value Binary Value
STX 02 0000 0010
ETX 03 0000 0011
ENQ 05 0000 0101
ACK 06 0000 0110
DLE 10 0001 0000
NAK 0F 0000 1111
(For the standard definition of these characters, refer to the ANSI
X3.4, CCITT V.3, and ISO 646 standards.)
A symbol is a sequence of one or more bytes having a specific
meaning to the link protocol. The component characters of a
symbol must be sent one after another with no other characters
between them. DF1 protocol combines the characters listed in the
tables above into control and data symbols:
•
Control symbols are fixed symbols required by the DF1 protocol
to read a particular message
•
Data symbols are variable symbols which contain the application
data for a particular message
Transmission Symbols