Communication
FPΣ User's Manual
198
POU Header and LD Body
ST Body
8.6.5 Flag Operation in Program Controlled Communication
Program controlled communication provides for half duplex communication, i.e.
communication is possible in both directions, but not simultaneously. Sending can be
controlled by the "transmission done" flag. Reception can be controlled by the "reception
done" flag or by directly evaluating the receive buffer.
The flags are special internal relays which turn to TRUE or to FALSE under specific
conditions. They can be evaluated using special functions or system variables.
"Reception done" flag
When the end code is received, the "reception done" flag turns to TRUE. Reception of any
further data is prohibited. F159_MTRN turns the "reception done" flag to FALSE.
The "reception done" flag can be evaluated using the IsReceptionDone function. Or use the
system variable sys_bIsComPort1ReceptionDone, sys_bIsComPort2ReceptionDone, or
sys_bIsToolPortReceptionDone, depending on the port. The end of reception can also be
determined by time-out using the IsReceptionDoneByTimeOut function or by checking the
contents of the receive buffer.
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.
Port
name
Port
number
Special
internal
relay
Function name System variable name
Bit
status
TOOL 0 R903E sys_bIsToolPortReceptionDone
COM1 1 R9038 sys_bIsComPort1ReceptionDone
COM2 2 R9048
IsReceptionDone
sys_bIsComPort2ReceptionDone
TRUE
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