RF-Link Technology NL6000 manual Serial Connection to an I/O Device, Carrier Sense Multiple Access

5.6.5.Carrier Sense Multiple Access

If a unit￿s transmit and receive frequencies are the same, it may be helpful to enable Carrier Sense Multiple Access (CSMA). This option does not allow transmission of a packet until the channel is free of contention.

5.7.Serial Connection to an I/O Device

5.7.1.Basic Serial Parameters

The NL6000 can receive data strings from a variety of I/O devices through its RS232 serial port. Configure the NL6000 serial port parameters based upon how the I/O device will send data to the unit. The following is a list of the basic serial parameters you must configure:

∙Baud rate ￿ This parameter is the data rate between the I/O device and the NL6000 modem. Set the baud rate to the rate of the I/O device.

∙Data bits ￿ This parameter is the number of bits the I/O device sends in a byte. The options available are 7 or 8. The NL6000 does not use parity bits.

∙Stop bits ￿ This parameter is the number of bits used for the end of a byte. The options available are 1 or 2.

∙Transmit Character Timeout ￿ The NL6000 transmits a data packet on the radio channel when there is a timeout on the serial port equal to this value or when the amount of data in the input buffer is equal to the Maximum Packet Size.

5.7.2.Flow Control

Prior to configuration of the NL6000, determine if you want to use flow control to prevent the serial device or modem from overflowing its buffer. If flow control is desired, two types are available ￿ RTS/CTS and XON/XOFF. With RTS/CTS, the modem monitors the RTS signal to determine when to send data to the serial device. In addition, the modem asserts CTS when the modem is ready to accept data from the serial device. RTS/CTS is the preferred method of flow control, but it requires separate lines for RTS and CTS. If you cannot use hardware flow control, you may use the XON/XOFF software option for flow control. This option may only be used for ASCII data and requires the use of special characters to identify when it is OK to send/ receive data to/from the serial device.

5.7.3.DCD Mode

The DCD Mode parameter identifies how the I/O device interprets the current state of the modem using the DCD line between the device and the modem. If the mode is set to Enable, the modem asserts the DCD line when it is receiving data over-the-air. If the mode is set to Disable, the modem asserts the line when it is in a normal operating state and negates the line when it is in

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