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Data transfer via communication ports
POU Header and LD Body
ST Body
Data can be received when the "reception done" flag is FALSE. The "reception done" flag is evaluated by the
system variable sys_bIsComPort1ReceptionDone. When the reception of the data is complete (the end code
has been received), the "reception done" flag turns to TRUE, and subsequently, receiving data is prohibited. To
prepare the system to receive the next data without immediately sending further data, the receive buffer is reset
by executing F159_MTRN with n_Number = 0.
NOTE
The status of the "reception done" flag may change while a scan is being carried out. For example, if the
flag is used more than once as an input condition, different statuses may exist within one scan. To
ensure proper execution of the program, the status of the special internal relay should be copied to a
variable at the beginning of the program.
The start code "STX" resets the receive buffer. 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.
For details on the format of the data in the send buffer and in the receive buffer, please see "Format of
send and receive data" on page 745.
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