MICRF114 datasheet(9/34 Pages) MICROCHIP

9 / 34 page

 2015 Microchip Technology Inc.

Preliminary

DS50002416A-page 9

MICRF114

After the wake-up delay, the MICRF114 starts to

automatically transmit. Since the exact timing of this is

unknown by the MCU, keep the transmit data input low

until the maximum specified wake-up time passes.

Although the MICRF114 wakes up earlier, it transmits

‘0’, that is, no carrier. Transmit data is asynchronous

and directly modulates the RF carrier. The MCU takes

care of all timing and coding of the data in software.

This is feasible due to the typical low-data rates and is

necessary due to the great variety of proprietary

protocols. The flowchart in Figure 2-4 shows the

MICRF114 states during a normal operation cycle.

2.4

Parameter Selection

All transmit parameters of the MICRF114 are stored in

a single 16-bit register. This is loaded with default

values at POR. The MCU can modify these values

before sending the transmit data. There are four

distinct parameter fields in the register as shown in

Table 2-1. To keep the MCU interface simple, only the

complete register as a whole can be updated. Fields

that need to remain unchanged must be reloaded with

the same value. For example, the new register value is

retained in Sleep mode until the next POR event.

FIGURE 2-4:

TOP FLOWCHART

TABLE 2-1:

TRANSMIT PARAMETERS OF MICRF114

Bit Range

Parameter

Field

Symbol

Default

Setting

Value

<15:13>

Transmit Frequency

F<2:0>

fTX

0x7

425-445 MHz

<12:8>

Crystal Load Capacitor

X<4:0>

CXT

0x16

18 pF

<7:4>

RF Transmit Power

P<3:0>

PTX

0xC

+10 dBm

<3:0>

RF Output Tuning Capacitor

R<3:0>

CTX

0x0

0 pF

SLEEP

TRANSMIT

Start?

CFG = 1?

CAL = 1?

Read

Control Bits

Read

Config Bits

Stop?

Calibration

Wake-up

Sequence A

Wake-up

Sequence B

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