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MELSEC-F
WHEN COMMUNICATING DATA USING THE MC PROTOCOL9
9 - 7
9.1.3 Contents of data designation items
This section explains the data items of commands and responses when
communicating using MC protocol.
In the response that is returned by the Ethernet module to an external device, the
data is automatically specified by the Ethernet module; the user does not need to
specify it.
(1) Header
The header for TCP/IP or UDP/IP is used. The user does not need to specify it at
the PLC side; the Ethernet module attaches it.
(2) Subheader
The format of the subheader is configured as follows.
(3) PC number
The PC number is fixed at a value of "FFH".
(a) When communicating in binary code, the PC number is expressed in binary
value.
(b) When communicating in ASCII code, the PC number is expressed in
hexadecimal ASCII code.
(4) Monitoring timer
This is a timer for setting the period of time that the Ethernet module should wait
after outputting a read/write request to the PLC until the result is returned.
(a) Specify the value as shown below.
0000
H (0): : Waits infinitely
*1
0001 to FFFFH (1 to 65535) : Wait time (in units of 250 ms)
*1 It keeps waiting until a response is returned from the PLC.
(b) For normal data communications, using a value within the setting range of 1
to 40 (0.25 to 10s) is recommended.
(5) Character field (command)
This data contains the Ethernet module commands that indicate functions for
when an external device reads/writes data from/to the target PLC station.
The contents and order of data in the Character field (command) field differ
depending on the function used.
The order of data items for each function is explained in each function's reference
section in Subsection 9.3.2. and later.
B7 B6 B5 B4 B3 B2 B1 B0
Command/response type
(This differs for each function. For details,
see Section 9.2 and later.)
Command/response flag
For command: 0
For response: 1