Control Contents Of Dc Code Control - Mitsubishi MELSEC L Series User Manual

7.2 Control Contents of DC Code Control

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This control uses the Q series C24 transmission control data to inform the external
device whether or not local station is ready to receive data and the valid range of the
send and receive data.
The four kinds of Q series C24 DC code control shown below are available. These
control functions can be used simultaneously.
(1) DC1/DC3 transmission control, DC1/DC3 reception control
The Q series C24 informs the external device whether or not local station is ready
to receive data by transmitting the DC1 and DC3 signals and checks whether or
not the external device is ready to receive data by receiving the DC1 and DC3
signals.
DC1...Control data that informs the external device that the Q series C24 is ready
to receive data
DC3... Control data that informs the external device that the Q series C24 is not
ready to receive data
(Example)
External device Data 1-1
Programmable
controller CPU
(a) Q Series C24 DC1/DC3 transmission control and free OS area specification
The control is performed in the same as those described in Section 7.1 (1)
DTR control and the free OS area specification are the same as those
described in Section 7.1 (1) (b).
The Q series C24 transmits DC1 or DC3 to the external device instead of
turning the ER (DTR) signal on/off.
For the DC1 and DC3 transmit timing, replace ER (DTR) signal ON/OFF as
listed below.
(DTR control)
ER (DTR) signal OFF= DC3 transmit ...... Transmitted when the vacant OS
ER (DTR) signal ON = DC1 transmit ....... Transmitted when the vacant OS
External device
Programmable
controller CPU
7 DATA COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL
(Terminate)
(Restart)...Continue
Data 1-2
D D
C C
3 1
(DC1, DC3 transmission control)
Data
D
C
3
D D
C C
3 1
Data 2-1 Data 2-2
(Terminate) (Restart)...Continue
area drops to 64 bytes (default) or
less
area reaches 263 bytes (default)
or more
Data
D
C
1
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