Communication
FPΣ User's Manual
194
communication port from an external device, operation takes place as follows. (The "reception
done" flag turns to FALSE after switching to RUN mode.)
• Incoming data is stored in the receive buffer. Start and end codes are not stored in the
receive buffer. The storage area for the data received starts with the second word of
the receive buffer (offset 1). Offset 0 contains the number of bytes received. The initial
value of offset 0 is 0.
1
Storage area for the number of bytes
received
0
1
2
n
Offset
2
1
3
4
2n 2n-1
2
Storage area for the data received
Bold numbers indicate the order of reception.
• When the end code is received, the "reception done" flag turns to TRUE. Reception of
any further data is prohibited. The "reception done" flag only turns to TRUE if an end
code, e.g. CR, has been selected in the system registers.
3. Processing the data in the receive buffer
• Verify the end of reception.
• Copy the data in the receive buffer to a target area defined in the program using a
transfer instruction, e.g. F10_BKMV.
NOTE
For details on the operation of the "reception done" flag, see page 198
4. Preparing the system for the reception of further data
In order to receive the next data, reset the receive buffer. This is done automatically when
sending the next data with F159_MTRN:
• Resetting the receive buffer sets the number of bytes received in offset 0 to 0 and
moves the write pointer back to offset 1. Subsequent data will be stored in the receive
buffer starting at offset 1. (The receive buffer is not cleared).
• The "reception done" flag turns to FALSE.
To reset the receive buffer without sending further data, execute F159_MTRN with n_Number
= 0.
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