Basic Principles of Serial Data Transmission
2.7 Data transmission with the printer driver
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
78
Manual, 09/2008, A5E02191071-01
Data flow control/Handshaking
Handshaking controls the data flow between two communication partners. Handshaking
ensures that data is not lost in transmissions between devices that work at different speeds.
You can also send message texts with data flow control during printout. There are essentially
two types of handshaking:
●
Software handshaking (e.g., XON/XOFF)
●
Hardware handshaking (e.g., RTS/CTS)
Data flow control is implemented as follows on the CP 341 during printout:
●
As soon as the CP 341 is assigned for operation with flow control, it sends the XON
character or sets the RTS line to ON.
●
CP 341 interrupts the output of characters when it receives the XOFF character, or when
control signal CTS = OFF is set. If neither an XON character is received nor CTS is set to
ON once a configured time has elapsed, printout is canceled and an appropriate error
message (0708H) is generated at the STATUS output of the SFB PRINT.
Note
When RTS/CTS flow control is assigned, you must fully wire the interface signals in the
plug connection.
BUSY signal
The CP 341 evaluates the printer's "BUSY" control signal. The printer signals to the CP 341
that it is ready to receive:
●
For CP 341-20mA-TTY: With current on RxD line
●
For CP 341–RS 232C and CP 341-RS 422/485: CTS signal = "ON".
Note
When RTS/CTS flow control is assigned, you must set the polarity of the BUSY signal on
the printer as follows:
•
BUSY signal: CTS = "OFF"
Note that some printers use the DTR signal to display the BUSY signal. In such cases
you must wire the cable to the CP 341 appropriately.
See also
RS 232C Interface of the CP 341-RS 232C (Page 221)
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