XE1203I063 データシートの表示（PDF） - Unspecified

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XE1203I063

433MHz / 868MHz / 915MHz Low-power, integrated UHF transceiver

Unspecified 

Data Sheet

XE1203

5.4 SELECTION OF THE REFERENCE FREQUENCY

The reference clock used for the frequency synthesizer and internal digital circuit can be generated internally using

internal amplifier and external quartz crystal or provided by an external oscillator. In the case of external oscillator,

the register “RTParam_Osc” has to be set high, and the external clock signal at 39 MHz has to be applied to the

pin “XTA”.

The chip can be used with a 39 MHz quartz crystal running on its fundamental frequency or with 3rd overtone

frequency. The third overtone operation requires a resistor in parallel to the quartz. This resistor can be selected by

programming the register ADParam_Resxosc(3:0). The required value depends on the crystal used.

ADParam_Resxosc(3:0) is set to ”0000’’ by default, which imposes a resistor of 3.8 MOhms in parallel to the

crystal. This default value is used with a 39 MHz crystal running on its fundamental frequency. In the case of

overtone operation of the quartz crystal, where the microcontroller uses the XE1203 as a clock source, user should

be aware that during power up the XE1203 oscillator starts at fundamental frequency and after programming the

oscillator switch to overtone operation. Therefore, a wait can be required for the oscillator to settle down before

doing time sensitive operations.

5.5 CLOCK OUTPUT INTERFACE

When RTParam_Clkout is set high, a frequency divider by 4, 8, 16, 32, depending on ADParam_Clkfreq is

embedded in the chip and provides the CLKOUT clock signal for an MCU or an external circuitry. The input

frequency of this divider is the 39.0 MHz reference frequency, so the possible output frequencies are listed in the

next table.

ADParam_Clkfreq

00

01

10

11

CLKOUT frequency

1.22 MHz

2.44 MHz

4.87 MHz

9.75 MHz

When the XE1203 is in sleep mode, then this clock is stopped even if RTParam_Clkout remains high.

5.6 DEFAULT SETTINGS AT POWER-UP

The internally generated power on reset signal sets the RTParam, FSParam, ADParam and Pattern registers to

00hex. Only exception is CLKOUT generation, although RTPAram_CLkout is set to low, i.e disabled, the XE1203

generates a CLKOUT signal in order to let the microcontroller operate.

The first rising edge on EN pin causes the registers to be updated and this will result CLKOUT to be disabled. For

this reason the first programming sequence should be enabling CLKOUT by setting RTPAram_CLkout register to

high for applications using CLKOUT. Initializing the XE1203 registers immediately after power-up according to the

application needs is strongly recommended.

32

D0308-214

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