MICRF114 datasheet(7/34 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

Preliminary

DS50002416A-page 7

MICRF114

2.0

FUNCTIONAL DESCRIPTION

2.1

Initialization

After applying the supply voltage, the MICRF114 is

initialized by its built-in POR circuit. The POR is level

sensitive. It starts to generate a Reset pulse for the

internal logic when the rising supply voltage (VDD)

crosses a given threshold. The threshold level is

chosen so that the operation of the digital circuits is

already guaranteed at the beginning of the Reset

pulse.

Initialization first involves resetting all internal state

machines, setting the Configuration register to its

default value, and executing a calibration sequence to

guarantee

proper

operation

the

frequency

synthesizer. Blocks needed for calibration are turned

on with the required sequence and timing. The result is

stored after calibration, and all blocks are turned off to

bring the MICRF114 into Sleep mode where it waits for

the MCU to initiate transmission. The calibration result

is kept as long as the supply voltage is present.

Figure 2-1

illustrates

the

simplified

initialization

flowchart where the Reset due to VDD drops or brown-

out is not shown. Additionally, it is not shown that a

Reset condition in any state or during any sequence

immediately brings the MICRF114 into its Reset state.

One of the advantages of the level-sensitive Reset is

that the generation and length of the Reset pulse are

mostly independent of the slope of the rising VDD.

Another advantage is that it triggers a Brown-out Reset

(BOR) when VDD goes below the VTP threshold

voltage. Refer to Figure 2-2.

Abrupt drops of the VDD can disturb the operation of

digital circuits even if the VDD always stays above the

threshold level during such a transient. The POR block

also generates a Reset pulse after this kind of event if

the voltage drop exceeds the VTG threshold value.

FIGURE 2-1:

INITIALIZATION FLOWCHART

2.2

Operating Modes

The MICRF114 has two main operating modes:

•Sleep mode

• Transmit mode

In Sleep mode, all the blocks (except the POR and the

digital block) are powered down and wait to be woken

up by the MCU. The current consumption is minimal

because there is no activity within the digital block.

After the wake-up sequence and the associated delay,

MICRF114 enters Transmit mode. In Transmit mode,

all blocks become active and an RF signal, modulated

by the data stream sent by the MCU, is transmitted.

Transmission can be terminated by the MCU without

any time-out delay when required and the MICRF114

immediately goes back to Sleep mode.

Section 2.3 “Communication with the MCU” shows

the main operating mode flowchart and the associated

activity on the MCU interface.

FIGURE 2-2:

POR OPERATION

calibration

SLEEP

VDD>VTP?

wake-up

sequence A

RESET

PORn

VDD

VTP

VTG

VLO

VHI

tDP

Note: VHI follows VDD

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