Only some UART types support the Flow control directly on the chip. Use the 16950 emulation to allow rich possibilities.
Get this panel after selecting "Software" Flow control in the standard settings of the port. Otherwise the control elements are inactive.
- Transmit control Enable
- This enables the automatic control when sending data.
If the receiving device sends a stop (Xoff) signal, transmission is halted. When a continue (Xon) signal is received, transmission continues. This reduces the probability of sending to much data to the receiver.
This does not need any processing by the main processor. - Transmit control Xon/Xoff Character
- The special characters acting as continue and stop signals as above.
Normally stop (Xoff) is a ^S (dez: 19, hex: $13), continue (Xon) is a ^Q (dez: 17, hex: $11).
You should not change these values. - Receive control Enable
- This enables the automatic control when receiving data.
When to much data is received and not read by the processor, the UART generates a stop signal to the other side. When enough data is read by the processor, the UART generates a continue signal. - Receive control Xon/Xoff Character
- Same function as above.
Even when it is possible to use other values than above, we strongly recommend to use the standard values. - Receive control Triggers Xon
- The level when the UART generates the continue signal.
When the processor reads the received data, the amount remaining in the UART will fall below this limit. At that time the continue signal is issued to the other side. - Receive control Triggers Xoff
- The level when the UART generates the stop signal.
When this amount of data is received and stored in the FIFO, the UART issues the stop signal to hold further transmission by the other side.
This value must be higher than the Xon Trigger. Depending on the global situation (processor speed, system load, transmission parameters, transmitting device, ...) possible values can be: 32 (quarter of FIFO) for Xon and 64 (half) for Xoff.
To Contents
This panel configures the On-Chip RTS/CTS Hardware Flow Control provided by the UART.
The function of this panel is similar to the software Flow control panel. However, the stop and start signals are provided by the RTS and CTS signals. RTS controls the input direction, while CTS controls output.
Basics of hardware flow control:
When CTS is asserted by the other side, transmission is allowed. If deasserted, transmission is halted.
When the system is ready to receive data, it asserts the RTS line to the other side. If it needs a pause, it deasserts RTS.
This panel is only available when "Hardware Flow control" is previously selected in the standard settings of the port.
- RTS Enable
- Selects the On-Chip receive Flow control.
- RTS on
- Function is similar to the Xon slider from above.
- RTS off
- Function is similar to the Xoff slider from above.
- CTS Enable
- Selects the On-Chip transmit Flow control.
To Contents