CC2500-RTR1 datasheet(40/99 Pages) TI1

40 / 99 page

CC2500

SWRS040C

Page 40 of 89

19.1.1 Automatic POR

A power-on reset circuit is included in the

CC2500. The minimum requirements stated in

Section 4.9 must be followed for the power-on

reset to function properly. The internal power-

up sequence is completed when CHIP_RDYn

goes low. CHIP_RDYn is observed on the SO

pin after CSn is pulled low. See Section 10.1

for more details on CHIP_RDYn.

When the

CC2500 reset is completed the chip

will be in the IDLE state and the crystal

oscillator will be running. If the chip has had

sufficient time for the crystal oscillator to

stabilize after the power-on-reset, the SO pin

will go low immediately after taking CSn low. If

CSn

is taken low before reset is completed the

pin will first go high, indicating that the

crystal oscillator is not stabilized, before going

low as shown in Figure 16.

Figure 16: Power-On Reset

19.1.2 Manual Reset

The other global reset possibility on

CC2500 is

the SRES command strobe. By issuing this

strobe, all internal registers and states are set

to the default, IDLE state. The manual power-

up sequence is as follows (see Figure 17):



Set SCLK=1 and SI=0, to avoid potential

problems with pin control mode (see

Section 11.3 on page 26).



Strobe CSn low / high.



Hold CSn high for at least 40 µs relative to

pulling CSn low



Pull CSn low and wait for SO to go low

(CHIP_RDYn).



Issue the SRES strobe on the SI line.



When

goes

low

again,

reset

complete and the chip is in the IDLE state.

CSn

XOSC Stable

XOSC and voltage regulator switched on

SRES

40 us

Figure 17: Power-On Reset with SRES

Note that the above reset procedure is only

required just after the power supply is first

turned on. If the user wants to reset the

CC2500 after this, it is only necessary to issue

an SRES command strobe.

19.2

Crystal Control

The

crystal

oscillator

(XOSC)

either

automatically

controlled

always

on,

MCSM0.XOSC_FORCE_ON

is set.

In the automatic mode, the XOSC will be

turned off if the SXOFF or SPWD command

strobes are issued; the state machine then

goes to XOFF or SLEEP respectively. This

can only be done from the IDLE state. The

XOSC will be turned off when CSn is released

(goes high). The XOSC will be automatically

turned on again when CSn goes low. The state

machine will then go to the IDLE state. The SO

pin on the SPI interface must be pulled low

before the SPI interface is ready to be used;

as described in Section 10.1 on page 22.

If the XOSC is forced on, the crystal will

always stay on even in the SLEEP state.

Crystal oscillator start-up time depends on

crystal ESR and load capacitances. The

electrical specification for the crystal oscillator

can be found in Section 4.4 on page 12.

19.3

Voltage Regulator Control

The voltage regulator to the digital core is

controlled by the radio controller. When the

chip enters the SLEEP state, which is the state

with the lowest current consumption, the

voltage regulator is disabled. This occurs after

CSn

is released when a SPWD command

strobe has been sent on the SPI interface. The

chip is now in the SLEEP state. Setting CSn

low again will turn on the regulator and crystal

CC2500-RTR1 数据表(PDF) 40 Page - Texas Instruments

CC2500-RTR1 数据表(HTML) 40 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

数据表下载