Communication with External Devices
FP2 Serial Data Unit
4 − 13
4.3 Programming When Data is Received
6. The received buffer clear contact goes off.
At the timing at which the X1 (Reception completed flag) contact goes off, the Y11
(Received Buffer Clear) contact is turned off by the user’s program.
FP2
CPU unit
FP2 serial data unit
Shared memory
RS232C device
Data register
DT100
Reception completed (X1:on)
Received buffer cleared (Y11:on)
Received
buffer
Notes
• When consecutive data are received, the serial data unit
temporarily stores the data received through the RS232C port
in a port buffer, and after the end code has been received, the
data is sent to the received buffer of the shared memory.
• When consecutive data items are received
Between operation steps 2 and 6, data sent from the RS232C
device is stored in the port buffer. At the point when operation
step 6 has been completed, if there is a frame in the port buffer
that includes an end code, it is sent to the received buffer of
the shared memory, and the operation of operation step 1
begins.
RS232C device
Data reading using
F150(READ) instruction
FP2 CPU unit
End code received
Reception completed: on
The reception completed contact goes on at the point when the data is
transferred from the port buffer to the shared memory received buffer.
FP2 serial data unit
Data
receiving
Port buffer
Data
register
Received
buffer of
shared
memory
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