Tait TM8000 Series, Applications Manual

Page: 50 / 136

50 Programmable I/O Lines TM8000 3DK Hardware Developer’s Kit Application Manual
September 2003 © Tait Electronics Ltd
3.1.8 Toggle Tx RF Inhibit
Application
This input signal is used to prevent the RF carrier from being radiated while
in transmit mode. This can be used e.g. for precise timing of data
transmissions such as GPS.
Activation of one or more ‘ Toggle Tx RF Inhibit ’ input lines will inhibit
the radios transmitter PA from generating RF power. The radio is otherwise
unaffected by this input (i.e. the radio will still enter and exit transmit state,
indicate transmit to the user, time transmit duration, send signalling through
the transmit audio path and in all other respects act as per normal).
Configuration
Configure an input line and associate it with this action. Set the active state
(high or low) and the debounce time (0 to 100ms). This action can be
programmed to both the auxiliary and the internal options connector at the
same time (logical OR).
Timing
The input line has a response time of less than 2.5 ms.
If this line is activated within 300 µs following an activation of any one of the
PTT sources, the PTT action will not be initiated.
Description
When any ‘ Toggle Tx RF Inhibit ’ input line is activated and the radio is in
transmit mode (on any channel and independent of the type of
transmission), the radio will ramp down the RF power to <–10 dBm
(100µW), but it will remain in the transmit state.
If the input line is active while the radio is powered up, it must be re-applied
for the action to be carried out.
When all ‘ Toggle Tx RF Inhibit ’ input lines are deactivated and the radio
is in transmit mode, the radio will ramp up the RF power to its previous
setting.
If the radio starts transmission while one or more ‘ Toggle Tx RF Inhibit ’
input lines are active, the radio will enter transmit state as normal, but will
not ramp up the RF power.
The radio is able to leave the transmit state (e.g. to return to receive state)
irrespective of the state of the ‘
Toggle Tx RF Inhibit ’ input lines.
Figure 3.5 Toggle Tx RF Inhibit
TX processing chain
PA
modulator
AUX_MIC_AUD
audio tap points
(mapped from AUD_TAP_IN)
Tx audio path
mux
MIC_AUD
mute
Mute External
Audio Input
mute
Toggle Tx RF Inhibit