Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Bedienungsanleitung PDF herunterladen (Seite 152)

9–14 Diagnostic Counters

Publication

17706.5.16 - October 1996

Cat. Nos. Link Pages

1771KA, 1771KA2, and 1774KA DH 9-14, 9-15

1771KC DH 9-16, 9-18

1771KE/KF DH 9-8

1771KG, KGM DH 9-19

1771KA, 1771KA2, and 1774KA DH Diagnostic Counters

This counter byte Counts the number of

0 Times CRC was in error on an ACK.

1 Times the sender timed out waiting for an acknowledgement.

Common error that occurs with error reflections or noise on the link

(sensitive to problems on longer cables). It also shows up if the

receiver or transmitter circuitry on a module is marginal, or if cable

connections are loose.

2 Times contention was detected.

This appears quickly on noisy or long cables. This counter

corresponds to error 93. If 93 is a common error on your link,

expect 37 (start bit timeout) errors also, since any reply that

experiences contention is not retried.

3 Times the ACK was successfully received but contained a nonzero

status code other than memory full.

Only other implemented ACK code is buffer overflow. This condition

should never occur except when debugging new code.

4 Times the link driver returns a message to sender.

Each count corresponds to one local error bit set or one reply

message lost.

5 Times the receiving node's memory was full.

Each time this happens, the message is placed on a waiting queue

for 0.5s. Each message is retried five times for memory overflow

before it is returned to sender.

6 Times this node grabbed mastership of the DH link because it timed

out while waiting to hear a valid frame.

On a link that has just been powered up, there should be only one

node that has this counter incremented.

7 Times this node has tried to relinquish mastership and the node that

was expected to take over failed to respond.

Happens on a noisy link because the noise is mistaken for a poll

response, and the wrong node is selected as the next master.

When this occurs, the old master resumes polling.

Also happens on a long link, if the poll response is very attenuated

and is not picked up by the carrier detect circuit. If the new node

responds, but the old master does not hear it, the old master

records a false poll and continues polling. The new master starts

polling also. This usually leads to the second node detecting

contention and relinquishing.

8 Times the receiver received a status frame instead of a message

frame.

This occurs only if a poll timeout is imminent (a master has had

mastership for more than 170ms) and the node has disabled its

address recognizer to test for any valid traffic.

1771 Cat. Nos.

1 2 ... 147 148 149 150 151 152 153 154 155 156 157 ... 250 251

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