MRF49XA-ISLASHT datasheet(65/102 Pages) MICROCHIP

65 / 102 page

Preliminary

DS70590C-page 65

MRF49XA

3.16

Sleep, Wake-up and Battery

Operations

The advanced interrupt handler circuit is configured in

the transmitter to reduce the power consumption. As

mentioned, the Sleep mode is the lowest power

consumption mode in which the clock and all functional

blocks of the device are disabled. In case of any

interrupt, the device wakes up, switches to Active mode

and an interrupt signal generated on the IRO pin

indicates

the

change

state

the

host

microcontroller. The source of the interrupt can be

determined by reading the status word of the device

(see Register 2-1).

To reduce current consumption, the MRF49XA should

be placed in the low-power consuming Sleep mode. In

Sleep mode, the 10 MHz main oscillator is turned off,

disabling the RF and baseband circuitry. Data is

retained in the control and FIFO registers and the

transceiver is accessible through the SPI port.

The MRF49XA will not enter Sleep mode if any of the

interrupt remains active, irrespective of the state of the

OSCEN bit in the PMCREG. This way, the

microcontroller can always have a clock signal to

process the interrupt. To prevent high-current

consumption, which results in shorter battery life, it is

highly recommended to process and clear interrupts

before entering Sleep mode. The functions which are

not necessary should be turned off to avoid unwanted

interrupts.

To minimize the current consumption, the MRF49XA

supports different power-saving modes, along with an

integrated wake-up timer. Active mode can be

reinitiated by the following ways:

• By applying the wake-up events’ negative logical

pulse on INT pin

• Wake-up timer time-out

• Low supply voltage detection

• On-chip FIFO filled up

• On receiving a request through the serial interface

To make the MRF49XA device enter into Sleep mode,

certain control register values must be initialized. The

sequence to program the control registers for entering

into Sleep and Wake-up modes is as follows:

For Sleep mode:

Check the IRO bit status

Read STSREG

Configure GENCREG

Configure PMCREG for oscillator and clock

buffering

For Wake-up mode:

Enter in TX/RX mode or

Enable crystal or

Set the INT pin

The device has the ability to wake itself up from Sleep

mode through a wake-up timer. The WTSREG sets the

wake-up interval for the MRF49XA. After setting the

wake-up interval, the WUTEN bit (PMCREG<1>)

should be cleared and set at the end of every wake-up

cycle.

The Wake-up Duration Time (WUTIME) is calculated

as shown in Equation 3-4.

EQUATION 3-4:

The Battery Threshold Detect feature is useful in

monitoring the discharge-sensitive batteries, such as

Lithium cells. The LBDEN bit (PMCREG<2>) is used to

enable or disable the low battery detect feature.

The BCSREG configures the following:

• Output clock frequency

• Low battery detect threshold

The low battery threshold value is programmable from

2.2V to 3.8V and is calculated by using Equation 3-5.

EQUATION 3-5:

When the battery level falls 50 mV below this value, the

LBTD bit (STSREG<10>) is set, indicating that the

battery level is below the programmed threshold.

The registers associated with power-saving modes

are:

•STSREG (see Register 2-1)

• GENCREG (see Register 2-2)

• TXCREG (see Register 2-4)

• RXCREG (see Register 2-7)

• PMCREG (see Register 2-13)

• WTSREG (see Register 2-14)

• BCSREG (see Register 2-16)

WUTIME = 1.03 x WTMV<7:0> x 2WTEV<4:0> + 0.5 ms

where:

WTMV<7:0> = Decimal Value between 0 to 255

WTEV<4:0> = Decimal Value between 0 to 29

Note: WUTIME is measured in ms.

Threshold Voltage Value = 2.25 + 0.1 x (LBDVB<3:0>)

where:

LBDVB<3:0> is the Decimal Value from 0-15

MRF49XA-I/T Datasheet(PDF) 65 Page - Microchip Technology

MRF49XA-I/T Datasheet(HTML) 65 Page - Microchip Technology

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 99 100 ...More

Datasheet Descarga

Enlace URL