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SATEL OY
// SATELLAR MANUAL // RADIO UNIT // USER GUIDE // V. 1.8
6. Data transmission
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Data reception can not be blocked with Signal Threshold setting.
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NOTE! The Fast Mode selection is not available with 150 kHz channel.
6.6 Data flow control in basic and source routing mode
In this chapter is described what ways there are available to add control to the data flow in basic mode.
6.6.1 TX delay
TX delay can be used in a situation where a certain master station sends queries as broadcast messages
to many sub-stations. To prevent the replies from the sub-stations to collide at the master station, you can
set different TX delay values to each of the sub-stations. This means that a sub-station does not reply to
the query until the TX delay period has been expired. TX delay is fixed, i.e. the maximum length of the reply
message must be approximately known at the network configuration phase in order to really avoid colli-
sions at the master station. TX delay can be considered as a primitive time-slot mechanism.
6.6.2 Handshaking
The handshaking lines of the serial data interface can be used to control the data flow from/to the RU.
There are three different control lines for this purpose, namely CTS, RTS, and CD lines.
6.6.2.1 CTS (Clear To Send)
The CTS line is normally in the active state, which means that the RU is ready to accept data from the DTE.
When the RU sets the line to the inactive state the data transfer from the DTE to the RU is not possible.
There are four alternative criteria for the user to select when the CTS line goes to the inactive state. These
are explained in the table below:
Selection
Description
Clear to send
Goes to the inactive state in the following cases:
1) Data reception is ongoing.
2) A pause (packet end) has been detected in the transmitted data
and there is still data in the transmission buffer. The line shifts back
to the active state when the RU has finished the transmission.
3) Transmission buffer is in danger of overflowing.
TX buffer state
Goes to the inactive state only when the transmission buffer is in
danger of overflowing. This happens typically in cases where the
data rate of the serial interface is higher than the air speed.
