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MELSEC-
7 USING FRAMES WHEN EXCHANGING DATA
Special character
code
Details
DDH
During frame transmission, the remote register (RW) value is referred to. Two bytes of the value
are transmitted in the order of (binary value) low-order byte and high-order byte. The low-order byte
of the designated RW value is the first character, and the high-order byte is the second character.
FF
H
DD
H
RW
designation
*
1
(Example) When designated RW value is 16706 (4142H)
A
41
H
B
42
H
"RW" value is transmitted
Transmission
DEH to DFH Use prohibited
*1 Refer to section 2) for details on designating RX/RY/RW.
(d) Special characters for sum check codes
The special characters for sum check codes are used to transmit and
receive the sum check codes in a set range of the statement to enhance
the reliability of the data exchanged with an external device.
The sum check codes and details of data during transmission/reception are
shown below.
Special
character
code
Details of data during transmission/reception, and handling by R2
Transmission/
reception order
EEH
The low-order 2 bytes of the calculation sum check
code are transmitted/received as a 2-byte binary code.
Transmitted/received
in order of (L) (H)
EFH Use prohibited –
F0H
The low-order 1 byte of the calculation sum check
code are transmitted/received as a 1-byte binary code.
–
F1H
The low-order 1 byte of the calculation sum check
code is converted into a 2-digit ASCII code and
transmitted/received.
Transmitted/received
from highest digit
F2H Use prohibited –
F3H
The sum check codes in the
range, excluding the head frame
(1 frame worth) of the
transmission/reception data
(statement), are transmitted and
received.
The low-order 4 bits of the calculation sum check code
is converted into a 1-digit ASCII code and
transmitted/received.
–
F4H
The low-order 2 bytes of the calculation sum check
code are transmitted/received as a 2-byte binary code.
Transmitted/received
in order of (L) (H)
F5H Use prohibited –
F6H
The low-order 1 byte of the calculation sum check
code are transmitted/received as a 1-byte binary code.
–
F7H
The low-order 1 byte of the calculation sum check
code is converted into a 2-digit ASCII code and
transmitted/received.
Transmitted/received
from highest digit
F8H Use prohibited –
F9H
The low-order 4 bits of the calculation sum check code
is converted into a 1-digit ASCII code and
transmitted/received.
–
FAH
The sum check codes in the
range, including the head frame
(1 frame worth) of the
transmission/reception data
(statement), are transmitted and
received. *
1
The calculation sum check code is converted into a
complement of 2, and the low-order 1 byte of the value
is converted into a 2-digit ASCII code and
transmitted/received.
Transmitted/received
from highest digit
*1 If the head frame is not designated, the transmission/reception data section range will be calculated as the sum
check target.
