CC2500-RTY1 datasheet(41/96 Pages) TI

41 / 96 page

CC2500

SWRS040C

Page 41 of 89

oscillator and make the chip enter the IDLE

state.

When wake on radio is enabled, the WOR

module will control the voltage regulator as

described in Section 19.5.

19.4

Active Modes

CC2500 has two active modes: receive and

transmit. These modes are activated directly

by the MCU by using the SRX and STX

command strobes, or automatically by Wake

on Radio.

The frequency synthesizer must be calibrated

regularly.

CC2500 has one manual calibration

option (using the SCAL strobe), and three

automatic calibration options, controlled by the

MCSM0.FS_AUTOCAL

setting:



Calibrate when going from IDLE to either

RX or TX (or FSTXON)



Calibrate when going from either RX or TX

to IDLE automatically



Calibrate every fourth time when going

from either RX or TX to IDLE automatically

If the radio goes from TX or RX to IDLE by

issuing an SIDLE strobe, calibration will not be

performed. The calibration takes a constant

number of XOSC cycles (see Table 28 for

timing details).

When RX is activated, the chip will remain in

receive mode until a packet is successfully

received or the RX termination timer expires

(see Section 19.7). Note: the probability that a

false sync word is detected can be reduced by

using PQT, CS, maximum sync word length

and sync word qualifier mode as describe in

Section 17. After a packet is successfully

received the radio controller will then go to the

state indicated by the MCSM1.RXOFF_MODE

setting. The possible destinations are:



IDLE



FSTXON: Frequency synthesizer on and

ready at the TX frequency. Activate TX

with STX.



TX: Start sending preambles



RX: Start search for a new packet

Similarly, when TX is active the chip will

remain in the TX state until the current packet

has been successfully transmitted. Then the

state

will

change

indicated

the

MCSM1.TXOFF_MODE

setting. The possible

destinations are the same as for RX.

The MCU can manually change the state from

RX to TX and vice versa by using the

command strobes. If the radio controller is

currently in transmit and the SRX strobe is

used, the current transmission will be ended

and the transition to RX will be done.

If the radio controller is in RX when the STX or

SFSTXON

command strobes are used, the TX-

if-CCA function will be used. If the channel is

not clear, the chip will remain in RX. The

MCSM1.CCA_MODE

setting

controls

the

conditions for clear channel assessment. See

Section 17.5 on page 37 for details.

The SIDLE command strobe can always be

used to force the radio controller to go to the

IDLE state.

19.5

Wake On Radio (WOR)

The

optional

Wake

Radio

(WOR)

functionality enables

CC2500 to periodically

wake up from SLEEP and listen for incoming

packets without MCU interaction.

When the SWOR strobe command is sent on

the SPI interface, the

CC2500 will go to the

SLEEP state when CSn is released. The RC

oscillator must be enabled before the WOR

strobe can be used, as it is the clock source

for the WOR timer. The on-chip timer will set

CC2500 into the IDLE state and then the RX

state. After a programmable time in RX, the

chip goes back to the SLEEP state, unless a

packet is received. See Figure 18 and Section

19.7 for details on how the timeout works.

Set the

CC2500 into the IDLE state to exit

WOR mode.

CC2500 can be set up to signal the MCU that a

packet has been received by using the GDO

pins.

packet

received,

the

MCSM1.RXOFF_MODE

will

determine

the

behaviour at the end of the received packet.

When the MCU has read the packet, it can put

the chip back into SLEEP with the SWOR strobe

from the IDLE state. The FIFO will lose its

contents in the SLEEP state.

The WOR timer has two events, Event 0 and

Event 1. In the SLEEP state with WOR

activated, reaching Event 0 will turn on the

digital regulator and start the crystal oscillator.

CC2500-RTY1 数据表(PDF) 41 Page - Texas Instruments

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