CC1110-RTR1 datasheet(170/203 Pages) TI

170 / 203 page

CC1110

CC1110 PRELIMINARY Datasheet (Rev. 1.01) SWRS033A

Page 170 of 202

MCSM2.RX_TIME_RSSI function can be used.

The radio controller will then terminate RX if

the first valid carrier sense sample indicates no

carrier (RSSI below threshold). See Section

15.10.3 on page 166 for details on Carrier

Sense.

For OOK modulation, lack of carrier sense is

only considered valid after eight symbol

periods. Thus, the MCSM2.RX_TIME_RSSI

function can be used in OOK mode when the

distance between “1” symbols is 8 or less.

If RX terminates due to no carrier sense when

the MCSM2.RX_TIME_RSSI function is used,

or if no sync word was found when using the

MCSM2.RX_TIME timeout function, the chip

will always go back to IDLE. Otherwise, the

MCSM1.RXOFF_MODE setting determines the

state to go to when RX ends.

15.13 Frequency Programming

The frequency programming in

CC1110 is

designed

minimize

the

programming

needed in a channel-oriented system.

To set up a system with channel numbers, the

desired channel spacing is programmed with

the

MDMCFG0.CHANSPC_M

and

MDMCFG1.CHANSPC_E registers. The channel

spacing registers are mantissa and exponent

respectively.

The base or start frequency is set by the 24 bit

frequency word located in the FREQ2, FREQ1

and FREQ0 registers. This word will typically

be set to the centre of the lowest channel

frequency that is to be used.

The desired channel number is programmed

with the 8-bit channel number register,

CHANNR.CHAN, which is multiplied by the

channel offset. The resultant carrier frequency

is given by the expression shown below.

()

)

256

(

−

⋅

CHANSPC

XOSC

carrier

CHANSPC

CHAN

FREQ

With a 26 MHz crystal the maximum channel

spacing is 405 kHz. To get e.g. 1 MHz channel

spacing one solution is to use 333 kHz

channel spacing and select each third channel

in CHANNR.CHAN.

The preferred IF frequency is programmed

with the FSCTRL1.FREQ_IF register. The IF

frequency is given by:

FREQ

XOSC

210

⋅

Note that the SmartRF

Studio software

automatically

calculates

the

optimum

FSCTRL1.FREQ_IF register setting based on

channel spacing and channel filter bandwidth.

If any frequency programming register is

altered when the frequency synthesizer is

running,

the

synthesizer

may

give

undesired response. Hence, the frequency

programming should only be updated when

the radio is in the IDLE state.

15.14 VCO

The VCO is completely integrated on-chip.

15.14.1 VCO and PLL Self-Calibration

The VCO characteristics will vary with

temperature and supply voltage changes, as

well as the desired operating frequency. In

order to ensure reliable operation,

CC1110

includes frequency synthesizer self-calibration

circuitry. This calibration should be done

regularly, and must be performed after turning

on power and before using a new frequency

(or channel). The number of XOSC cycles for

completing the PLL calibration is given in

Table 48 on page 169.

The calibration can be initiated automatically

manually.

The

synthesizer

can

automatically

calibrated

each

time

the

synthesizer is turned on, or each time the

synthesizer is turned off. This is configured

with the MCSM0.FS_AUTOCAL register setting.

In manual mode, the calibration is initiated

when the SCAL command strobe is activated

in the IDLE mode.

Note that the calibration values are maintained

power-down

modes

PM2/3,

the

calibration is still valid after waking up from

these power-down modes (unless supply

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