CC1100-RTR1 datasheet(45/100 Pages) TI1

45 / 100 page

CC1100

SWRS038D

Page 45 of 92

The time between two consecutive Event 0 is

programmed with a mantissa value given by

WOREVT1.EVENT0

and WOREVT0.EVENT0,

and

exponent

value

set

WORCTRL.WOR_RES

. The equation is:

RES

WOR

XOSC

Event

EVENT

750

⋅

The Event 1 timeout is programmed with

WORCTRL.EVENT1

. Figure 19 shows the

timing relationship between Event 0 timeout

and Event 1 timeout.

Figure 19: Event 0 and Event 1 Relationship

The time from the

CC1100 enters SLEEP state

until the next Event0 is programmed to appear

(tSLEEP in Figure 19) should be larger than

11.08 ms when using a 26 MHz crystal and

10.67 ms when a 27 MHz crystal is used. If

tSLEEP is less than 11.08 (10.67) ms there is a

chance that the consecutive Event 0 will occur

128

750 ⋅

XOSC

seconds

too early. Application Note AN047 [4] explains

in detail the theory of operation and the

different registers involved when using WOR,

as well as highlighting important aspects when

using WOR mode.

19.5.1 RC Oscillator and Timing

The frequency of the low-power RC oscillator

used for the WOR functionality varies with

temperature and supply voltage. In order to

keep the frequency as accurate as possible,

the RC oscillator will be calibrated whenever

possible, which is when the XOSC is running

and the chip is not in the SLEEP state. When

the power and XOSC is enabled, the clock

used by the WOR timer is a divided XOSC

clock. When the chip goes to the sleep state,

the RC oscillator will use the last valid

calibration result. The frequency of the RC

oscillator is locked to the main crystal

frequency divided by 750.

In applications where the radio wakes up very

often, typically several times every second, it

is possible to do the RC oscillator calibration

once

and

then

turn

off

calibration

(WORCTRL.RC_CAL=0) to reduce the current

consumption. This requires that RC oscillator

calibration values are read from registers

RCCTRL0_STATUS

and RCCTRL1_STATUS

and written back to RCCTRL0 and RCCTRL1

respectively. If the RC oscillator calibration is

turned off it will have to be manually turned on

again if temperature and supply voltage

changes.

Refer to Application Note AN047 [4] for further

details.

19.6 Timing

The radio controller controls most of the timing

CC1100, such as synthesizer calibration, PLL

lock time, and RX/TX turnaround times. Timing

from IDLE to RX and IDLE to TX is constant,

dependent on the auto calibration setting.

RX/TX and TX/RX turnaround times are

constant. The calibration time is constant

18739 clock periods. Table 28 shows timing in

crystal clock cycles for key state transitions.

Power on time and XOSC start-up times are

variable, but within the limits stated in Table 7.

Note that in a frequency hopping spread

spectrum or a multi-channel protocol the

calibration time can be reduced from 721 µs to

approximately 150 µs. This is explained in

Section 32.2.

Description

XOSC

Periods

26 MHz

Crystal

IDLE to RX, no calibration

2298

88.4µs

IDLE to RX, with calibration

~21037

809µs

IDLE to TX/FSTXON, no

calibration

2298

88.4µs

IDLE to TX/FSTXON, with

calibration

~21037

809µs

TX to RX switch

560

21.5µs

RX to TX switch

250

9.6µs

RX or TX to IDLE, no calibration

0.1µs

RX or TX to IDLE, with calibration

~18739

721µs

Manual calibration

~18739

721µs

Table 28: State Transition Timing

CC1100-RTR1 Datasheet(PDF) 45 Page - Texas Instruments

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