192 ACQ550-U1 User’s Manual
Embedded fieldbus
Diagnostics – EFB
Fault queue for drive diagnostics
For general ACQ550 diagnostics information, see Diagnostics on page 251. The 
three most recent ACQ550 faults are reported to the fieldbus as defined below. For 
specific ACQ550 fault codes, see Fault listing on page 252.
Serial communication diagnostics
Network problems can be caused by multiple sources. Some of these sources are:
• Loose connections
• Incorrect wiring (including swapped wires)
• Bad grounding
• Duplicate station numbers
• Incorrect setup of drives or other devices on the network
The major diagnostic features for fault tracing on an EFB network include Group 53 
EFB Protocol parameters 5306…5309. The Complete parameter descriptions 
section describes these parameters in detail.
Diagnostic situations
The sub-sections below describe various diagnostic situations – the problem 
symptoms and corrective actions.
Normal operation
During normal network operation, 5306…5309 parameter values act as follows at 
each drive:
• 5306 
EFB OK MESSAGES advances (advances for each application message 
properly received and addressed to this drive).
• 5307 
EFB CRC ERRORS does not advance at all (advances when an invalid 
message CRC is received).
• 5308 
EFB UART ERRORS does not advance at all (advances when character format 
errors are detected, such as parity or framing errors).
• 5309 
EFB status value varies depending on network traffic.
• BACnet protocol: 5316 
EFB PAR 16 (MS/TP token counter) advances for each 
token passed to this drive. (Does not apply for other protocols.)
Drive Parameter
Protocol Reference
Modbus BACnet
0401 Last Fault 40401 AV18
0412 Previous Fault 1 40402 AV19
0413 Previous Fault 2 40403 AV20