Communication with External Devices
FP2 Serial Data Unit
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4.3 Programming When Data is Received
Operation steps when data is received
When data is received by the serial data unit, operation is carried out in the following
steps.
1. Reception completed of data
Data received from the RS232C port is stored in the received buffer of the shared
memory in the serial data unit at the point when the end code is received.
Shared memory
Received buffer
Data receiving
RS232C device
FP2
CPU unit
FP2 serial data unit
2. The reception completed flag goes on.
If the data is received with no problems, the X1 (Reception completed flag) contact of
the serial data unit goes on, to notify the CPU unit that reception has been completed.
Shared memory
RS232C device
FP2
CPU unit
FP2 serial data unit
Reception completed (X1:on)
Received buffer
3. The data is read from the shared memory.
At the timing at which the X1 (Reception completed flag) contact goes on, the F150
(READ) instruction of the user’s program is used to read the data to the data register.
Received
buffer
FP2
CPU unit
FP2 serial data unit
Shared memory
Data reading using F150(READ) instruction
RS232C device
Data register
DT100
Reception completed (X1:on)
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