CC2400-RTR1 datasheet(34/84 Pages) TI1

34 / 84 page

CC2400

SWRS042A

Page 34 of 83

25 Radio control state machine

CC2400 has a built-in state machine that is

used to switch between different operation

states (modes). The change of state is

done either by writing to command strobe

registers, or using dedicated pins.

Before using the radio in either RX or TX

mode, the main crystal oscillator must be

turned on and become stable. The crystal

oscillator has a start-up time given in

Table 8, during which its output is gated

internally

avoid

timing

problems

stemming from too narrow clock pulses.

The crystal oscillator is controlled by

accessing

the

SXOSCON/SXOSCOFF

command

strobe

registers.

The

XOSC16M_STABLE

bit

the

status

indicates whether the oscillator is running

and stable or not (See Table 13). This

status register can be polled when waiting

for the oscillator to start.

The frequency synthesizer (FS) can be

started by either accessing the command

strobe register SFSON or by using the RX

and TX control pins. The FS will then enter

its

self-calibration

mode.

After

the

calibration is performed, the FS needs to

lock onto the right LO frequency. The

calibration and lock acquisition time is

given in Table 8.

When the FS is in lock it is possible to go

into RX or TX mode. That can be done

either

accessing

the

SRX/STX

command strobe registers, or by using the

RX and TX control pins. It is possible to

change quickly between TX and RX by

way of the FS On state.

Turning off RF can be accomplished by

either accessing the command strobe

TX control pins. When using the RX and

TX pins to go from the FS On to Radio Off

it is important that TX is set to 0 before RX

is set to 0.

The state transitions using the RX and TX

pins are illustrated in Figure 15.

Note that to switch between RX and TX,

the FSDIV register must be updated. This

is because direct conversion is used in TX

mode, while an IF frequency of 1 MHz is

used in RX mode. Please see page 47 for

information

about

frequency

programming.

Also note that the FSDIV register should

only be changed when the radio is in IDLE

mode, otherwise the PLL can go out of

lock.

CC2400-RTR1 数据表(PDF) 34 Page - Texas Instruments

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