Sending Data To The External Device; Transmission Methods - Mitsubishi Melsec-L Series User Manual

11.2 Sending Data to the External Device

11.2.1 Transmission methods

CPU module
Sequence
program
1)
Write
(BIDOUT
instruction)
Send instruction
BIDOUT instruction
completion device
BIDOUT instruction
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This section explains the data transmission from the CPU module to an external device.
The following shows the method of sending data to the external device through data
communication using the bidirectional protocol.
C24
Buffer memory
Transmission area
2)
Data
(00 to FF )
H H
5)
Transmission
completed
Contents
CH1/CH2
1) Data such as control data and transmission data are stored in the device designated
with the BIDOUT instruction and then the BIDOUT instruction is executed.
2) The transmission data count and transmission data are written into the
transmission area of the buffer memory.
3) The C24 sends data by adding the control code ENQ at the beginning of the data.
When "Exist" is specified for "Sum check code" in Switch Setting of GX Works2,
the C24 adds the sum check code calculated by internal processing to the end
of the message and then transmits the message.
When "None" is specified in the Switch Setting of GX Works2, no sum check
code is sent.
4) A response for the data transmission (for normal completion: ACK message; for
abnormal completion: NAK message) is received.
5) The execution of the BIDOUT instruction completes with the transmission
processing completion of the C24.
11 DATA COMMUNICATION USING THE BIDIRECTIONAL PROTOCOL
3)
Sum check code Data portion
(00
4)
ACK
NAK Error code
Control timing
BIDOUT
Any data
Data length ENQ
to FF )
H H
(When normal)
(When abnormal)
External
device
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