Rockwell Automation 1758-RTU202 DataSite Software User Manual FRN 1.2 - Manual (Page 63)

Publication 1758-UM002D-EN-P - October 2010
DataSite Configuration Settings Utility (DS Settings) 63
Variable and Command
Each piece of HART equipment is designed differently. For example, when
you use command 3 to read variables from HART equipment, the four
dynamic variables returned may have different meanings, and not all four
variables may be valid. Refer to the documentation for the HART equipment
for more information. See also the table,
Description of HART commands .
Response Message
The response message of a piece of HART equipment contains the Err Num
and Err State values. The Err Num value indicates the number of times
communication with the HART equipment has failed. The Err State value
indicates whether communication with the HART equipment is a success or
failure. An Err State value of 0 means that communication with HART
equipment is successful. An Err State value of 1 means that the
communication with HART equipment has failed.
You can also read the response code from the HART equipment. It is stored
as two bytes in the state register which you have configured in the HART scan
block. If bit 7 in the first byte is 1, this byte is bit-mapped and all the
communication errors are displayed in this byte. If bit 7 in the first byte is 0,
this byte is not bit-mapped and the meaning is determined by the value of bit 6
through bit 0.
Unit register +0 = Transmit variable code, 8-bit unsigned integer
+1 = Transmit variable limits units code, 8-bit unsigned integer
HART state register +0 = state 0
+1 = state 1
Command 59
Purpose Write Number of Responses Preambles
Send register +0 = Number of preambles to be sent with the Response message
from the Slave to the Master, 8-bit unsigned integer, between 5
and 20
Return register Not used
Unit register Not used
HART state register +0 = state 0
+1 = state 1
Description of HART commands (Continued)