Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 153)

9–15 Diagnostic Counters
Publication 1770Ć6.5.16 - October 1996
This counter byte Counts the number of
9
Frames that were rejected because the header was incomplete.
This is counted only because of undebugged software or in the
unlikely event that a bad frame fooled the CRC checker.
10 Frames that were rejected because the destination address was
incorrect.
This can have the same cause as counter byte 8. This counter also
detects frames that have the same source and destination address.
11 Times the receiver sent an ACK without first being able to allocate a
receive buffer.
This results in a memory overflow error when the next message is
received.
12 Frames rejected because of a bad CRC.
This error is very common on a noisy DH link.
13 Times a message was received that contained more than 250 bytes.
14 Times a message was received when there was no buffer space
allocated for it (usually follows a memory full error).
15 Duplicate frames received.
A duplicate frame is sent by a transmitter when it fails to receive an
ACK. If the reason it failed to receive an ACK was that the ACK was
lostĊrather than because the original message was lostĊ
the duplicate is redundant and is discarded. Any two successive
messages between polls that have the same sequence number
fields and the same command or reply bits are assumed to be
duplicates.
16 Aborts received.
The HDLC abort signal is not used on a DH link, but can be
detected by the serial input or output, in certain circumstances.
Some nodes whose addresses match the ringing pattern after a
transmitter shutoff are susceptible to this error (nodes 36, 76, and
176, for example). These numbers depend on highway
configurations.
17, 18 Messages successfully transmitted.
19, 20 Messages successfully received.
21, 22 Command messages that were successfully generated as a result of
a start bit being set and records this number.
Some command messages may not be recorded because they were
not successfully sent or they were sent back to the originating node.
23, 24 Command messages that were received to be executed a the link.
This count does not depend on whether execution was successful.
For each message counted as received a reply message is sent.
25, 26 Reply messages received that resulted in the setting of a done or
remote error bit.
27 Breaks sent to the industrial terminal.
28 Times the PLC driver has to reĆsynchronize with the PLC processor.
This counter always counts at least one reĆsynch (because of
powerup).
29 Errors on the KAĆtoĆIT cable (counts down module 5).
Every time this count reaches zero, the 1771ĆKA does a handshake
to reset the forced I/O table in the PLC processor.