ABB Relion 620 Series - Modbus TCP;IP Diagnostic Counters; Supported Modbus Function Codes; Application Functions

3.2.2.1 Modbus TCP/IP diagnostic counters
Modbus TCP/IP counters can be viewed via the LHMI path Monitoring/
Communication/Modbus/MBS0n.
The counters show the complete Modbus protocol link frames and Modbus errors. The
Ethernet communication driver maintains its own counters for lower level
communication diagnostics.
Table 5: TCP/IP diagnostic counters
Counter Description
Status Shows the value "True" if the TCP/IP or serial instance is in use. This means
that a Modbus client has connected to the TCP socket and Modbus TCP
messages are received regularly at least with a 30 second interval or faster. In
all other cases this value shows "False".
Reset counters
True = Reset all diagnostic counters
Received frames Total amount of received Modbus frames.
Transmitted frames Total amount of transmitted Modbus responses.
Transmitted exc A Total amount of exception responses 1 and 2. These exception responses
usually reveal configuration errors on the Modbus client’s side.
Transmitted exc B Total amount of exception responses 3. These exceptions reveal the IED
application level rejections.
The counters are reset when the client makes a TCP socket disconnection or if the TCP
socket connection keep alive times out.
Table 6: Common (instance independent) Modbus TCP/IP diagnostic counters
Counter
Description
CnReject no sockets The amount of connection requests that are rejected due to unavailable TCP
sockets.
CnReject
unregistered
The amount of connection requests that are rejected since the client is not
registered.
3.3 Supported Modbus function codes
3.3.1 Application functions
Table 7: Supported application functions
Function
code
Name Description
01 Read coil status Reads the status of discrete outputs.
02 Read digital input status Reads the status of discrete inputs.
03 Read holding registers Reads the contents of output registers.
04 Read input registers Reads the contents of input registers.
Table continues on next page
1MRS757645 B Section 3
Vendor-specific implementation
620 series 19
Communication Protocol Manual