3.2.12 Serial link diagnostics and monitoring
Serial communication diagnostics and monitoring is divided between the serial link
driver and the serial communication protocol. The lower-level physical and protocol-
independent aspects of the UART-based serial communication are monitored in the
serial link driver. Diagnostic counters and monitoring values are located on the HMI
under Monitoring> Communication> COMn (n= 1,2,…).
Depending on the communication protocol, the serial driver software receives single
characters or complete protocol frames, based on the frame start/stop characters
or on link frame timing.
Table 41: Setting parameters
Parameter Description
Fiber mode Defines the fiber-optic mode used. Setting "No fiber" is the
same as galvanic mode.
Serial mode Used for galvanic RS-485 modes 2- or 4-wire. This setting is
relevant only if Fiber mode is set to "No fiber".
Baudrate Communication speed used.
Table 42: Diagnostic counters and indications
Counters Description
Characters received Counts all incoming non-erroneous characters. This counter
operates regardless of whether the serial driver is set to de-
tect a whole protocol link frame or just separate characters.
Frames received Counts all protocol-specific non-erroneous frames received.
Protocol-specific frames can be based on timing (for exam-
ple, Modbus RTU) or on special start and stop characters (for
example, Modbus ASCII).
Frames discarded Counts all protocol-specific erroneous frames received. If the
driver detects an error while receiving a frame, the whole
frame is automatically discarded. This also means that the
protocol in question never receives a faulty link frame from
the driver. When this counter is incremented, one of the de-
tailed error counters (Parity, Overrun, Framing) can also be
incremented.
Frames transmitted Counts all protocol-specific frames transmitted from the
COM channel.
Collisions Counts the number of transmission collisions that have oc-
curred. Used in RS-485 mode by some protocols where trans-
missions could collide with reception. For example, DNP3 un-
solicited reporting mode.
Parity errors Counts the number of parity errors detected in characters
received.
Overrun errors Counts the number of overrun errors detected in characters
received.
Framing errors Counts the number of framing errors detected in characters
received.
Link status In write direction: By writing value 1 to this parameter, all the
diagnostic counters are reset to 0.
Link status In monitoring direction: If the driver instance is in use by any
communication protocol, the monitoring value shows value
1. Otherwise, the value is 0.
Basic functions 1MRS759142 F
94 REX640
Technical Manual
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