Rockwell Automation 1770-HT8 SMART TRANSMITTER - Manual (Page 102)

Chapter 4
C Communicating with the Smart
Transmitter Interface
4-37
In full duplex mode, the host computer and Smart Transmitter Interface
can transmit and receive simultaneously. Once the Smart Transmitter
Interface receives a command, it can send the response to the host as soon
as it is available, without waiting for the host to request the response with a
separate command. Figure 4.13 and Figure 4.14 illustrate the format and
give an example of a full duplex DF1 command.
In half duplex mode, the master station controls which station can transmit.
The master station must also issue poll requests to the Smart Transmitter
Interface before the Smart Transmitter Interface will send a response.
Figure 4.15 and Figure 4.16 illustrate the format and an example of a half
duplex DF1 Command.
Figure 4.13
Full Duplex DF1 Packet sent by a Host Computer to the Smart Transmitter Interface
DLE
9007
STX DST SRC APPLICATION DATA DLE ETX BCC/CRC
CMD STS TNS FNC
SCMD CHN CTL PRM DATA
LEN DATA
Smart Transmitter
Interface Packet
Data Link
Layer Packet
Since message is from host to Smart Transmitter Interface
DLE = data link escape control character (10" hex)
STX = start of text control character (02" hex)
DST = Smart Transmitter Interface station address in hexadecimal
SRC = host station address in hexadecimal
CMD = OF" hexadecimal
STS = Status byte
TNS = transaction number (2 bytes)
FNC = 95" hexadecimal
LEN = length of Smart Transmitter Interface Packet in bytes
SCMD = Smart Transmitter Interface Command
CHN = Smart Transmitter Interface Channel
CTL = Smart Transmitter Interface Control
PRM = Smart Transmitter Interface Parameter
ETX = end of text control character (04" hex)
BCC/CRC = Block Check or CRC bytes
DF1 Packet Formation