9-8Communicating 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).

Publication 1785-UM012D-EN-P - July 2005

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Bradley Smoker PLC-5 user manual Monitoring Data Sent with Acknowledgment