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MELSEC-
A
7 USING FRAMES WHEN EXCHANGING DATA
(b) Functions of special characters, and usability during
transmission/reception
Usability
Transmission Reception
Frame
transmission
(Frame -1)
Frame
reception
Special
character code
Function during transmission/reception
Head End
Frame
transmission
(Frame -2)
Monitor
transmission
Head End
0H
During transmission:
The data code 00H (NUL) data (1 byte) is
transmitted.
During reception:
The check of the section corresponding to the
registration frame (1 byte worth) is skipped.
(Received as normal data.)
1H to BFH Use prohibited –
C0H to DFH
Data in a random registration frame is transmitted
according to the RX and RY ON/OFF state and
RW value comparison.
Refer to (c) for details.
E0H to EDH Use prohibited –
EEH to FAH
The check sum corresponding to the designated
range of the statement is transmitted and received
for checking the statement to be transmitted or
received.
Refer to (d) for details.
FBH to FEH Use prohibited –
FFH The data code FFH data (1 byte) is received.
: Usable, : Not usable
(c) RX/RY/RW reference special characters
The RX/RY/RW reference special characters refer to the ON/OFF state of
the master station's designated remote input(RX)/remote output (RY), and
the remote register (RW) value, and transmit the designated registration
frame data according to the details.
The RX/RY/RW reference special characters are designated with the
following arrangement.
FF
H
Special character code RX/RY, RW designation
(Designation of registration frame, etc.)
1st byte 2nd byte 3rd, 4th byte 5th byte and followings