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MELSEC-
A
6 EXCHANGING DATA WITH AN EXTERNAL DEVICE
6.3.2 Receiving data from an external device
The method for receiving data from an external device using the buffer memory
automatic update function is explained in this section.
(1) Flow of process
The flow of the process for reading data received from an external device using
the buffer memory automatic update function is shown below.
R2
RS-232-C
Programmable controller CPU Master station
Bit device
Word device
Remote
input (RX)
Remote
output (RY)
Remote
input (RX)
Remote
output (RY)
2) Automatic write
Automatic
update
buffer
(reception
area)
Random area
1) Data reception
External
device
Trans-
mission
5) Reception read
complete ON
7) Reception read
complete OFF
4) Reception data
read
3) Reception normal/
error read request
ON
6) Reception normal/
error read request
OFF
Reception
area
OS reception
area
(2) Timing chart
3)
2)
4)
6) 7)
5)
1)
Reception normal/error
read request signal
(RXn2/RXn3)
R2
Word device
Master station Automatic update area
(transmission area)
Reception area
Reception read complete
signal (RYn2)
Carried out with sequence program
Carried out by R2
External device
OS reception area
Programmable
controller CPU