Hart; Hart Protocol - Siemens SIMATIC ET 200SP HA Equipment Manual

HART function
7.1 Use
7.1.2

HART

Definition
"HART" stands for "Highway Addressable Remote Transducer" = via communications addressable
remote field devices (sensor or measuring transducer or final controlling element).
The HART functionality also enables you to use the I/O module to exchange data with the
connected field devices. The HART protocol is generally accepted as a standard protocol for
communication with intelligent field devices: HART is a registered trademark of the HART
Communication Foundation (HCF), which owns all the rights to the HART protocol. You can find
detailed information about HART in the HART specification.
7.1.3

HART protocol

Definition
The HART protocol describes the physical form of the transfer: transfer procedures, message
structure, data formats and commands.
Description
Each HART message frame sent from the analog module to the connected field device (request
frame) and each HART message frame received from the field device (response frame) has the
following basic structure.
PREAMBLE
PREAMBLE:
STRT:
ADDR:
COM:
BCNT:
STATUS:
DATA:
CHK:
With the exception of the preamble bytes, this structure is contained in the communication data
of the HART command interface.
HART job and response data records (Page 74)
38
STRT ADDR COM
Bytes (0xFF) for synchronizing.
5 bytes
Start character (start delimiter)
Address of the field device (1-byte; short address or 5-byte; long address)
HART command number
Byte count, number of bytes to follow without checksum
HART device status (1st and 2nd status byte). Only present for a response frame.
HART device status (Page 41)
Transferred user data / parameters, quantity depending on command (0...230
bytes)
Checksum
BCNT STATUS
Equipment Manual, 07/2022, A5E50101523-AB
DATA CHK
AI 4xI 2-/4-wire HART ISOL HA