Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 140)

Publication 1785-UM012D-EN-P - July 2005
9-8 Communicating with Devices on a DH+ Link
Monitoring Data Sent with Acknowledgment
Status Field Word(s) Description
Received 19 Number of error-free SDA messages that the station received.
Received SAP off 23 Number of SDA messages that the station received but could not process because its service
access point (SAP) was off.
This counter should always be 0.
Received but full 22 Number of SDA messages that the station could not receive because of lack of memory.
Received with error 20 Number of invalid SDA messages that the station received. Some causes are:
bad CRC
the message has an invalid source address
the message has an unrecognizable control byte
the transmission was aborted
This counter indicates noise; increase the cable’s shielding from noise.
Received retransmissions 21 Number of times the sending station re-transmitted an SDA message, which was ACKed or
NAKed
If node sends a message but does not receive an ACK or a NAK response, the node will
re-transmit the message. If a node retransmitted a message because the acknowledge response
to the first message was lost, the node receiving the message detects the retransmission and
sends an acknowledge response. But the receiving node discards the duplicate message. High
counts of this counter indicates noise or cable problems; check that the cable is secure and
properly shielded from noise.
Transmit failed 29 Number of SDA messages sent by the station that were determined to be in error. This counter is
the sum of the SDA transmit not ACKed and SDA transmit timeout counters.
Transmit timeout 26 The number of SDA messages that were sent but not ACKed or NAKed by the receiving station
This counter increments even if the message does get through during a retry and if the receiving
station is unable to communicate. This counter indicates a noise or a cabling problem (the
receiving station is not seeing the messages).