FX651 datasheet(4/16 Pages) CMLMICRO

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SPM and Security Subsystem

FX651

D/651/4

1.3

Signal List

Package

Signal

Description

Pin No.

Name

Type

XTAL

I/P

The input to the on-chip oscillator inverter.

XTALN

O/P

The inverted output of the on-chip oscillator.

To use, a crystal of frequency 3.579545MHz

should be connected between these two pins.

No other external components are necessary.

CLKIN

I/P

A logic input which may be used when an

external clock signal is available in place of a

crystal. The external 3.579545MHz signal is

applied to this pin and XTAL is tied to VDD.

When not used, this pin should be tied to VDD.

RX/TXN

I/P

A logic input which controls the operating mode

of the device. In Rx, the device detects the

presence of 12kHz and 18kHz tones. In Tx, the

18kHz detect function is disabled and 18kHz is

transmitted from the TXOP pin modulated ON -

OFF by the NRZ Data pin.

NRZ DATA

I/P

A logic input used in Tx mode to ASK modulate

the TXOP pin. A logic high corresponds to no

tone and logic low corresponds to 18kHz.

TXOP

O/P

The Tx mode output. It is ASK modulated by the

NRZ data input pin. It transmits 18kHz or no

tone depending upon the state of the NRZ data

input pin. This pin goes to a high impedance

state when in Rx mode.

8VSS

POWER

Negative supply rail.

9VBIAS

O/P

A bias line for the internal circuitry, held at

½ VDD. It also forms the analogue ground for

the input differential amplifier. This pin must be

decoupled by a capacitor mounted close to the

device pins (see Figure 1).

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