Response code and field device status, Response code – Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules User Manual
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Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
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Additional HART Protocol Information Appendix C
Response Code and
Field Device Status
Two bytes of status also called the response code and field device status are
included in every reply message from a field or slave device. These two bytes
convey communication errors, command response problems, and field device
status. If an error is detected in the outgoing communication, the most significant
bit (bit 7) of the first byte is set to 1 and the details of the error are reported in the
rest of that byte. The second byte is then all zeros.
Communication errors are typically those that would be detected by a UART
(parity overrun and framing errors). The field device also reports overflow of its
receive buffer and any discrepancy between the message content and the
checksum received.
In RSLogix 5000 software, if the leftmost bit of the ResponseCode is set, it
displays a negative number. In this case, the ResponseCode represents a
communication fault. Change the display format to hexadecimal to interpret
communication status.
If the leftmost bit of the ResponseCode is 0 (value 0…127), then there was no
communication error and the value is a ResponseCode from the HART field
device. Response codes indicate if the device performed the command. 0 means
no error. Other values are errors or warnings. To understand the ResponseCode,
contact your HART field device manufacturer or the HART specification.
See
for descriptions of the response code and the field device status.
Table 73 - Response Codes and Field Device Status
Response Code
Description
If Bit 7 is And Bits
6…0 are
1
16#40
Parity Error
Vertical parity error - The parity of one or more of the bytes received by the device was not odd
1
16#20
Overrun Error
Overrun error - At least one byte of data in the receive buffer of the UART was overwritten before it was
read (for example, the slave did not process incoming byte fast enough)
1
16#10
Framing Error
Framing error - The Stop Bit of one or more bytes received by the device was not detected by the UART (for
example, a mark or 1 was not detected when a Stop Bit should have occurred)
1
16#08
Checksum Error
Longitudinal parity error - The Longitudinal Parity calculated by the device did not match the Check Byte at
the end of the message
1
16#04
(Reserved)
Reserved - Set to zero
1
16#02
RX Buffer Overflow Buffer overflow - The message was too long for the receive buffer of the define
1
16#01
(undefined)
Reserved - Set to zero
0
0
No command specific error
0
1
(undefined)
0
3
Value too large
0
4
Value too small
0
5
Not enough bytes in command
0
6
Transmitter-specific command error
0
7
In Write-protect mode