SATELLINE-EASy / SATELLINE-EASy 869
User Guide, Version 3.0
24
The maximum absolute time is always 170 ms independent from the value of the Pause length
given in the set-up.
An increase in the Pause length increases the round trip delay of the radio link correspondingly;
this is due to the fact that the radio channel is occupied for the time of the Pause length after
each transmission (the time it takes to detect a pause). If this is not acceptable, the TX delay
setting may also be useful in special cases.
4.8
Data buffering
Whenever the radio modem is in
Data Transfer Mode
it monitors both the radio channel and the
serial interface. When the terminal device starts data transmission the radio modem switches to
transmission mode. At the beginning of each transmission a synchronisation signal is transmitted
and this signal is detected by another radio modem, which then switches into receive mode.
During the transmission of the synchronisation signal the radio modem buffers data into its
memory. Transmission ends when a pause is detected in the data sent by the terminal device,
and after all buffered data has been transmitted. When the serial interface speed is the same or
slower than the speed of the radio interface, the internal transmit buffer memory cannot
overflow. However, when the serial interface speed exceeds the speed of the radio interface,
data will eventually fill transmit buffer memory. In this instance, it will take a moment after the
terminal device has stopped transmission of data for the radio modem to empty the buffer and
before the transmitter switches off. The maximum size of transmit buffer memory is one kilobyte
(1 kB). If the terminal device does not follow the status of the CTS-line and transmits too much
data to the radio modem, the buffer will be emptied and the transmission is restarted.
In the receive mode, the buffer works principally in the above described way thus evening out
differences in data transfer speeds. If the terminal device transmits data to a radio modem in
receive mode, the data will go into transmit buffer memory. Transmission will start immediately
when the radio channel is available.
