4. Configuration
94
Direct
Representation
Variable
Diagnostic Variable
T_DIAG_MODBUS_RTU_SLAVE_1 *.
Communication Statistics:
Counter of normal requests received
by the slave and answered normally. In
case of a broadcast command, this
counter is incremented, but it is not
transmitted (0 to 65535)
Counter of normal requests received
by the slave and answered with
exception code. In case of a broadcast
command, this counter is incremented,
but it isn’t transmitted (0 to 65535).
Exception codes:
1: the function code (FC) is legal, but
not supported
2: relation not found in these MODBUS
data
3: illegal value for this field
128: the master/client hasn’t right for
writing or reading
129: the MODBUS relation is disabled
Counter of frames received by the
slave. It’s considered a frame
something which is processed and it is
followed by a Minimum Interframe
Silence, in other words, an illegal
message is also computed (0 to
65535)
Illegal request counter. These are
frames which start with address 0
(broadcast) or with the MODBUS slave
address, but aren’t legal requests –
invalid syntax, smaller frames, invalid
CRC – (0 to 65535)
Counter of frames with overrun errors
during reception – UART FIFO or RX
line – (0 to 65535).
Counter of frames with construction
errors, parity or failure during reception
(0 to 65535).
Counter of CTS time-out error, using
the RTS/CTS handshake, during the
transmission (0 to 65535).
Table 4-58. MODBUS RTU Slave Diagnostic
Note:
Counters: all MODBUS RTU Slave diagnostics counters return to zero when the limit value 65535
is exceeded.
Configuration of the Relations – Symbolic Mapping Setting
The MODBUS mapping configuration, depicted on Figure 4-24 follow the parameters described on
Table 4-59.
Figure 4-24. MODBUS Data Mappings Screen
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General