Panasonic FP2

FP2 Serial Data Unit
Functions of Serial Data Unit
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1.2 Function of Serial Data Unit
1.2 Function of Serial Data Unit
The CPU unit and serial data unit handle reading and writing of data through a shared
memory installed in the serial data unit.
When data is read from and written to the CPU unit and the serial data unit via the shared
memory in the latter, it is done using the F151 (WRT) and F150 (READ) instructions in
a ladder program. Handshaking with the CPU unit, transmission of error signals and
other functions are handled by X and Y contacts allocated to the serial data unit.
FP2 CPU unit
FP2 serial data unit
Shared memory
RS232C device
On/off of contact
Communication is carried out by controlling contacts such
as the “Reception Completed flag” and “Sending Directive”
allocated to the serial data unit.
Reading and writing of data
Data is read from and written to the
shared memory in the serial data
unit using the F150 (READ) and
F151 (WRT) instructions.
Data sending and reception
Data sending to and from external devices con-
nected to the RS232C port is handled through
the shared memory in the serial data unit.
FP2 serial data unit
Shared memory
Data reception
Data is read using
the F150 (READ)
instruction
“Reception completed flag” contact goes on
FP2
CPU unit
FP2 serial data unit
Shared memory
Data sending
RS232C
device
“Sending directive” contact goes on
Data is written using
the F151 (WRT)
instruction
RS232C
device
Reading data
Data input from the RS232C port is stored
in a received buffer in the shared memory,
and the “Reception Completed flag” is
turned on. This data is then read using the
F150 (READ) instruction of the ladder
program, and is stored in the data regis-
ters of the CPU unit and other areas.
Writing data
After the data to be output is written to the
sent buffer in the shared memory, using
the F151 (WRT) instruction, the “Send-
ing Directive” contact is turned on. This
causes the data to be output from the
RS232C port.
FP2
CPU unit