FPΣ User's Manual
8.6 Program Controlled Communication
197
pointer back to offset 1. Subsequent data will be stored in the receive buffer
starting at offset 1.
• For details on the format of the data in the send buffer and in the receive
buffer, please see "
Data Format" on page 197.
8.6.4 Data Format
Remember the following when accessing data in the send and receive buffers:
• The format of the data in the send buffer depends on the data type of the transmission
data (e.g. STRING) and on the conversion function used in the PLC program (e.g.
F95_ASC). There is no conversion when data in the send buffer is sent.
• The start and end codes specified in the system registers are automatically added to
the data sent. The start code is added at the beginning, the end code at the end of the
send string. Do not include start or end codes in the send string.
• The format of the data in the receive buffer depends on the data format used by the
external device. Use a conversion function to convert the data into the desired format,
e.g. F27_AHEX.
• Start and end codes in the data received are recognized if the corresponding start and
end codes have been specified in the system registers. Start and end codes are not
stored in the receive buffer. The end code serves as a reception done condition, i.e.,
the "reception done" flag turns to TRUE when the end code is received. The start code
resets the receive buffer.
• If "None" is selected for the start code, a start code is not added to the data sent and
is not recognized in the data received. Without start code, the receive buffer can only
be reset by executing F159_MTRN.
• If "None" is selected for the end code, an end code is not added to the data sent and
is not recognized in the data received. Without end code, the "reception done" flag
does not turn to TRUE. The end of reception can only be determined by a time-out
using the IsReceptionDoneByTimeOut function or by evaluating the data in the receive
buffer.
Different end code settings for sending and receiving
Sometimes you do not want to send an end code, but need an end code in the data received
to set the "reception done" flag to TRUE. In this case, select the desired end code in the
system registers and execute F159_MTRN specifying a negative number for n_Number.
EXAMPLE
Send 4 bytes of data without adding an end code:
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