MICRF114 datasheet(8/34 Pages) MICROCHIP

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MICRF114

DS50002416A-page 8

Preliminary

 2015 Microchip Technology Inc.

2.3

Communication with the MCU

The communication between the MCU and the

MICRF114 is one-directional and it is always initiated

by the MCU. It uses a proprietary protocol that supports

switching between the two operating modes, optional

request for recalibration, reprogramming of the

operating parameters (as needed), and transmit data

input. The logic is active-high.

The communications protocol requires both the lines of

Serial Clock (SCK) and Serial Data Input (SDI) to idle

high. However, this is not the state with the lowest

current consumption because the SCK input of the

MICRF114 has an internal pull-down resistor to avoid

unwanted clock transitions during the power-on

process. In Sleep mode, the clock line can be pulled

low to minimize the overall supply current.

Control and Configuration bits are sent synchronously

after the Start bit. The two control bits, CAL and CFG,

must always be present. If CAL is high, recalibration is

performed before transmission. In this case, the wake-

up time from Sleep mode to Transmit mode is longer. If

CFG is high, the MCU must send 17 additional

Configuration bits. The first 16 bits updates the 16-bit

Transmit Parameter register within the MICRF114. The

Most Significant bit (MSb) is sent first. The last bit must

always be ‘0’. Figure 2-3 shows the two methods of

starting transmission.

The wake-up sequence from Sleep mode to Transmit

mode starts at the rising edge of the last clock pulse.

This is the second or 19th clock, depending on the CFG

bit setting.

FIGURE 2-3:

COMMUNICATION PROTOCOL

Start

tWK + cal * tCL

SDI

Sleep

CAL

Transmit with quick-start using the default or previously loaded configuration settings.

SCK

CFG

Wake-up

Transmit

Asynchronous TX Data

Stop

(MCU Waits)

Sleep

Recalibration (CAL=1) is not normally needed.

Start

SDI

Sleep

CAL

Transmit start with configuration settings update.

SCK

CFG

Wake-up

16 Configuration (Config) bits

Recalibration is always needed in case of frequency setting change.

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