Specifications

Page 35
WT1231H
4. Operating Modes
4.1. Basic Modes
The circuit can be set in 5 different basic modes which are described in Table 16.
By default, when switching from a mode to another one, the sub-blocks are woken up according to a pre-defined and
optimized sequence. Alternatively, these operating modes can be selected directly by disabling the automatic sequencer
(SequencerOff in RegOpMode = 1).
Table 16 Basic Transceiver Modes
ListenOn
in RegOpMode
Mode
in RegOpMode
Selected mode Enabled blocks
0 0 0 0 Sleep Mode None
0 0 0 1 Stand-by Mode Top regulator and crystal oscillator
0 0 1 0 FS Mode Frequency synthesizer
0 0 1 1 Transmit Mode Frequency synthesizer and transmitter
0 1 0 0 Receive Mode Frequency synthesizer and receiver
1 x Listen Mode See Listen Mode, section 4.3
4.2. Aut
omatic Sequencer and Wake-Up Times
By default, when switching from one operating mode to another, the circuit takes care of the sequence of events in such
a way that the transition timing is optimized. For example, when switching from Sleep mode to Transmit mode, the
WT1231H goes first to Standby mode (XO started), then to frequency synthesizer mode, and finally, when the PLL
has locked, to transmit mode. Entering transmit mode is also made according to a predefined sequence starting with the
wake-up of the PA regulator before applying a ramp-up on the PA and generating the DCLK clock.
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The crystal oscillator wake-up time, TS_OSC, is directly related to the time for the crystal oscillator to reach its steady
state. It depends notably on the crystal characteristics.
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The frequency synthesizer wake-up time, TS_FS, is directly related to the time needed by the PLL to reach its steady
state. The signal PLL_LOCK, provided on an external pin, gives an indication of the lock status. It goes high when the
PLL reaches its locking range.
Fo
ur specific cases can be highlighted:
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Transmitter Wake Up time from Sleep mode = TS_OSC + TS_FS + TS_TR
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Receiver Wake Up time from Sleep mode = TS_OSC + TS_FS + TS_RE
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Receiver Wake Up time from Sleep mode, AGC enabled = TS_OSC + TS_FS + TS_RE_AGC
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Receiver Wake Up time from Sleep mode, AGC and AFC enabled = TS_OSC + TS_FS + TS_RE_AGC&AFC
Th
ese timings are detailed in sections 4.2.1 and 4.2.3.
In applications where the target average power c
onsumption, or the target startup time, do not require setting the
WT1231H in the lowest power modes (Sleep or Standby), the respective timings TS_OSC and TS_FS in the former
equations can be omitted.