Panasonic FP0R User Manual page 137

Communication
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 "Data format" on page 137.
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