4ć34 – Rockwell Automation 1770-HT8 SMART TRANSMITTER User Manual
Page 99
Communicating with the Smart
Transmitter Interface
Chapter 4
Communicating with the Smart Transmitter
Interface
4-34
Word 02: HART delimiter is hexadecimal 86 indicating an ACK frame
with a long frame address (low byte); HART long frame address is
hexadecimal A6 indicating primary master, burst mode disabled, and the
manufacturer’s identification code of hexadecimal 26 for Rosemount
(high byte).
Word 03: manufacturer’s device type code is hexadecimal 0D for a
3044C temperature transmitter (low byte); most significant byte of 24
bit device identification number is hexadecimal 00 (high byte).
Word 04: middle byte of 24 bit device identification number is
hexadecimal 15 (low byte); least significant byte is hexadecimal 11
(high byte).
Word 05: HART command is hexadecimal 01 (low byte); HART packet
byte count is hexadecimal 07 indicating 7 bytes of data between this
byte count and the check byte (high byte).
Word 06: first byte of HART response code is hexadecimal 00
indicating no communications errors (low byte); second byte of HART
response code is hexadecimal 00 indicating no device errors.
Word 07: primary variable units are hexadecimal 20 for degrees Celsius
(low byte); most significant byte of IEEE 754 primary variable is
hexadecimal 42 (high byte).
Word 08: second most significant byte of IEEE 754 primary variable is
hexadecimal 91 (low byte); third most significant byte of IEEE 754
primary variable is hexadecimal 39 (high byte).
Word 09: least significant byte of IEEE 754 primary variable is
hexadecimal 56 (low byte); HART packet check byte received is
hexadecimal B3 (high byte).
Serial communication between an RS-232C host and the Smart Transmitter
Interface is carried out using Allen-Bradley’s proprietary DF1 protocol.
DF1 is a full or half duplex protocol designed to carry messages intact over
a link. The protocol delimits messages, detects and signals errors, retries
after errors and controls message flow.
In a typical network as discussed in this manual, the host computer is the
master station and the Smart Transmitter Interface is the slave.
For a complete description of the DF1 protocol, you should see the Data
Highway/Data Highway Plus/DH-458 Protocol and Command Set Manual.
Serial Communication with the
Smart Transmitter Interface