Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 160)

160 Rockwell Automation Publication 1756-UM514C-EN-P - June 2014
Appendix A PCCC Commands Supported by the Data Highway Plus Module
Read DH+ Diagnostic Counters
Diagnostic counters are bytes of information stored in RAM in your
1756-DHRIO or1756-DHRIOXT module. The counters occupy a block of the
module’s internal scratch RAM. Your module’s counters wrap around to zero
when they overflow.
Counters are used to record events that can be used in debugging and long-term
reliability analysis. You must issue a diagnostic read to check the information in
your module’s counters.
CMD = 06h, FNC = 01
The definition of the data returned is shown in the following table.
Byte Description
0 Received ACK/NAK with bad CRC
1 Timeout expired with no ACK received
2 Transmit retries exhausted
3 Received NAK (illegal protocol operation)
4 Received NAK (bad LSAP)
5 Received NAK (no memory)
6 Received ACK/NAK too short
7 Received ACK/NAK too long
8 Received something other than ACK/NAK
9 Token pass timeout
10 Token pass retries exhausted
11 Claim token sequence entered
12 Token claimed
13 Received frame with bad CRC
14 Transmitted NAK (illegal protocol operation)
15 Transmitted NAK (bad LSAP)
16 Transmitted NAK (no memory)
17 Received frame too short
18 Received frame too long
19 Received retransmission of a frame
20 Received frame aborted
21 Message successfully sent (low byte)
22 Message successfully sent (high byte)
23 Message successfully received (low byte)
24 Message successfully received (high byte)
25 Command successfully sent (low byte)
26 Command successfully sent (high byte)
27 Reply successfully received (low byte)