Mitsubishi MELSEC L Series User Manual page 197

Programmable
controller CPU
Programmable
controller CPU
(3) The transmission control method and changing the DC code
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(a) Q series C24 DC2/DC4 transmission control contents
When transmitting data to an external device, the Q series C24 adds the
DC2 code to the head of the send data and the DC4 code to the end of the
send data.
External device
D
C
2
(b) Q series C24 DC2/DC4 reception control contents
1) When the Q series C24 receives DC2 from the external device, it
processes the receive data up to DC4 as valid data.
The sequence program cannot read the received DC2 code.
2) When the Q series C24 receives DC4, it ignores the receive data up to
immediately before DC2 as invalid data.
The sequence program cannot read the received DC4 code.
External device
3) Once DC2 is received, subsequent DC2 are ignored and are removed
from the receive data.
1 MC protocol A
compatible 1C frame
format 1
Switching between DC code control method and DTR/DSR control as well as
changing of the DC code are registered on the GX Configurator-SC's
"Transmission control and others system setting" screen.
7 DATA COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL
D
C
Data
4
Transmit order
(Non procedure protocol)
The DC2 and DC4 code are also added when MC protocol is used.
(Non procedure protocol)
D D
C C
Data
2 4
Stored to Q series C24
buffer memory or OS area
D E
External C N
device 2 Q
D E
C N
Data
2 Q
Transmit order
(Bidirectional protocol)
1
D
Arbitrary
C
data
2
Ignored by Stored to Q series C24
the Q series C24 buffer memory or OS area
D
C
4
D
C
Data
4
D
C
4
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