Spectrum Controls 1756sc-OF8H Series A - Manual (Page 166)

152 ControlLogix ™ Analog HART Modules
Status Status Status Status Status Two bytes of status, also called the response code, are included in every
reply message from a field or slave device. These two bytes convey three
types of information:
Communication errors
Command response problems
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.
If no error is detected in the outgoing communication, bit 7 of the first byte
is 0 and the remainder of the byte contains the command response, which
indicates any problem with the received command. The second byte
contains status information pertaining to the operational state of the field or
slave device.
Communication errors are typically those that would be detected by a
UART (i.e., 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.
Response Codes Response Codes Response Codes Response Codes Response Codes
Table 3a (Communication Status / First Byte) Table 3b (Communication Status / First Byte)
Bit 7 = 1: Communication Errors
Bit 6 Parity Error
Bit 5 Overrun Error
Bit 4 Framing Error
Bit 3 Checksum Error
Bit 2 (Reserved)
Bit 1 RX buffer overflow
Bit 0 (undefined)
Bit 7 = 0: Command Errors
Bit 6-0 (not bit-mapped):
0 No command specific error
1 (undefined)
2 Checksum Error
3 (Reserved)
4 RX buffer overflow
5 (undefined)
6 Transmitter-specific command error
7 In write-protect mode
8-15 Command-specific errors See table
below
16 Access restricted
32 Device is busy
64 Command not implemented