Rockwell Automation 1770-HT8 SMART TRANSMITTER - Manual (Page 79)

Communicating with the Smart
Transmitter Interface
Chapter 4
Communicating with the Smart Transmitter
Interface
4-14
Figure 4.8 illustrates the format of Smart Transmitter Interface packets
received by the Smart Transmitter Interface. The programmable controller
data files or host computer data buffers are formatted similarly for
transmission of data to the Smart Transmitter Interface. An optional Smart
Transmitter Interface Data field follows a required four-byte header. The
host processor places HART packets in the Smart Transmitter Interface
Data field when sending HART commands to a field device.
Figure 4.8
Smart Transmitter Interface Packets Ć Programmable Controller or Host Computer to
Smart Transmitter Interface
90075
No Response Required Bit
1 Response Not Required
0 0 0 0 0 0
Smart Transmitter Interface Command (Table 4.E)
Smart Transmitter Interface Channel Number (00 - 1F, FF)
Smart Transmitter Interface Control
Smart Transmitter Interface Parameter
Smart Transmitter Interface Data
0
Smart Transmitter Interface Command
The first byte of the header contains one of the valid commands listed in
Table 4.E. This command indicates to the Smart Transmitter Interface how
the remaining data in the header and the optional Smart Transmitter
Interface Data field should be processed.
Smart Transmitter Interface Channel
The second byte of the header contains the channel number that the host
processor wants to address. Each Smart Transmitter Interface supports up
to 32 channels. Address each of these using the hexadecimal numbers 00 to
1F. For commands intended for the Smart Transmitter Interface, rather than
a particular channel, use hexadecimal FF in this field.
Important: Address value hexadecimal 00 represents channel 1, address
value hexadecimal 01 represents channel 2, ..., address value hexadecimal
1F represents channel 32.
Smart Transmitter Interface
Packets Received by the
Smart Transmitter Interface