Communication
2.3 Modbus RTU Master
90 SICAM Q100, 7KG95xx, System Manual
E50417-C1040-C522-A8, Edition 09.2020
CRC error: a CRC error was detected in the response
PDU error: implausible response (for example, the requested number of
registers was not output)
• Name: Name of the Modbus slave device to which the request message belongs (as
for the Modbus device configuration).
• Device address: Device address of the Modbus slave device to which the request message
belongs (as for the Modbus device configuration).
• Function code: Modbus function code used in the request message (see Table 2-66).
• Start address: Start register address when reading data of this request message (based on the
register numbers of the Modbus mapping configuration).
• Qty. of registers: Number of registers requested in this message; this value is calculated auto-
matically based on the Modbus mapping configuration and the maximum regis-
ter gap parameters in the serial interface configuration.
• Scan cycle: Scan cycle (send cycle) currently used for this request message; either the con-
figured scan cycle is used for the data type or the configured "Scan cycle on
error".
• Last request: This value indicates how many ms ago the request message was last sent. Note
that this value is only intended as a notification that this message is sent and
when it was last sent. It is a snapshot referring to the last update of the diagnos-
tic page in the user interface. It cannot be used to determine the bus cycle time
exactly.
This value can be greater than the configured scan cycle. This means that there
is a longer delay in the bus cycle, for example, due to devices that are not re-
sponding.
• Data type: Data type requested with this request message (one or more data objects of this
data type were requested; different data types are always requested with sep-
arate messages, because they have different scan cycles).
• Bad messages: Counter for errors of this request:
No responses
Exception responses
CRC errors
SYS_SICAM_Q100_US.book Page 90 Thursday, September 24, 2020 1:17 PM
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