Dc2/Dc4 Transmission Control, Dc2/Dc4 Reception Control - Mitsubishi Electric MELSEC iQ-R Series User Manual

DC2/DC4 transmission control, DC2/DC4 reception control

C24 encloses the data transmitted from the host station in the DC2 and DC4 codes and transmits it to the target device, and
processes the data received from the target device enclosed in the DC2 and DC4 codes as valid data.
• DC2: Control data that informs the target device that the data following it is the start of the valid data
• DC4: Control data that informs the target device that the data immediately preceding it is the end of the valid data
Ex.
Target device DC2 Data
CPU module
C24 DC2/DC4 transmission control contents
When transmitting data to a target device, C24 adds the DC2 code to the head of the data to be transmitted and the DC4 code
to the end of the data to be transmitted.
Target device
CPU module
D
C
2
Transmit order
(Nonprocedural protocol)
C24 DC2/DC4 reception control contents
• When DC2 is received from the target device, C24 processes the received data up to DC4 as valid data.
The received DC2 cannot be read by the program.
• When DC4 is received from the target device, C24 ignores the received data up to the one immediately before DC2 as
invalid data.
The received DC4 cannot read by the program.
D
C
2
Target device
CPU module
Stored to C24 buffer memory
or OS area
*1 MC protocol 1C frame
D E
Target
C N
device
2 Q
• Once DC2 is received, subsequent DC2 is ignored and removed from the received data.
DC4
DC2 Data
D
C
Data
4
* The DC2 and DC4 code are also added for communication using MC protocol.
(Nonprocedural protocol)
D
Data Arbitrary data
C
4
Ignored by the C24
PC
No.
Character
11 DATA COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL
DC2 Data
DC4
D E D
C N C
Data
2 Q 4
Transmit order
(Bidirectional protocol)
*1
D
Data
C
2
Stored to C24 buffer memory
or OS area
D
C
4
11.2 Control Contents of DC Code Control
D
C
4
11
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