User's Manual

Page 51
E Series Ethernet Radio – User Manual
Version 08-10
• Xon/Xoff
If the ow control mechanism is XON/XOFF then
the modem uses the standard ASCII control codes
of DC1 {^Q=11(Hex)=17(Dec)} for XON and DC3
{^S=13(Hex)=19(Dec)} for XOFF. The DTR input line is totally
ignored.
Note: There is no substitution mechanism employed in the
XON/XOFF protocol, so care must be taken when transferring
binary data to ensure that invalid ow control characters are
not generated.
Advanced
This button provides access to the advanced features of the port
conguration. When selected a dialogue box appears which
Disabled
This selection disables the DCD output on the port. This selection
is not permissible if hardware based ow control has been
selected.
RF Carrier Detect
This selection causes DCD to be asserted at the onset of a an RF
signal that is higher than the mute setting. This will generally occur
several milliseconds before data is transmitted from the port.
Data Detect (RS485 Flow Control)
This selection causes DCD to be asserted when data is about
to be transmitted from the port. This option is not available if
handshaking is set to “None” or “Xon/Xoff”.
RF Parameters
This section of the main window permits adjustment of transmitter
and receiver, radio channel modulation scheme, frequency trim
and advanced features.
Part I – TVIEW+ Management Suite - Programmer
Handshaking (Packet Modes Only)
If the standard PAD is selected (i.e. Any settings apart from
SLIP/Diagnostics), then ow control can be either hardware
handshaking, XON/XOFF protocol or none.
The XON/XOFF ow control is not supported when using the SLIP/
Diagnostics protocol.
The Handshaking section of the screen allows the selection
of either of the handshaking methods as well as allowing
handshaking to be disabled.
Details of the two handshaking methods are given below.
Hardware
The modem acts as Data Communications Equipment (DCE) and
supplies to the host controller the following interface signals:
Data Set Ready (DSR)
Data Carrier Detect (DCD)
Clear To Send (CTS)
Receive Data Output (RXD)
The host controller must act as Data Terminal Equipment (DTE)
and supplies to the modem the following interface signals :
Data Terminal Ready (DTR)
Request To Send (RTS)
Transmit Data Input (TXD)
DCD: DCD has several modes of operation. It is set to TRUE
when data is being transferred from the modem to the host - RXD
line active. The signal is asserted approximately 500ms before the
start bit of the rst character in the data stream and remains for
approximately 1 character after the last bit in the data stream. The
other modes of operation are dependent on the advanced settings.
DSR: DSR is permanently set to TRUE.
CTS: The CTS is a signal from the modem to the host informing
the host that the modem is able to accept incoming data on the
TXD line. It responds to the actions of the RTS line similar to the
operation of a “standard” line modem.
The CTS is FALSE if the RTS line is FALSE. Once the RTS line is
set to TRUE (signalling that the host wants to send some data to
the modem on the TXD line), then the CTS will be set TRUE within
1ms, if the modem is capable of accepting more data.
The CTS line will be set to FALSE if the transmit buffer in the
modem exceeds 4075 bytes, or the number of queued frames
exceeds 29 to ensure that no overow condition can occur.
RTS: The RTS line is used for two reasons. The rst is to assert
the CTS line in response to RTS. The RTS line can also be used to
key up the transmitter stage of the modem.
DTR: The DTR line is used for ow control of data being sent
from the modem to the host controller. When the host is able to
accept data it sets this line to TRUE, and if data is available within
the modem, it will be sent to the host. If the host cannot accept
any more data, then it sets the DTR to FALSE, and the modem will
stop all transmissions to the host.
Permits selection of the source for the port DCD output signal.