PCD3316T datasheet(6/30 Pages) PHILIPS

6 / 30 page

Philips Semiconductors

PCD3316

CIDCW receiver

Product speciﬁcation

11 March 1999

6 of 30

9397 750 04824

The FSK-OVR Error bit (Status register, bit 3) indicates that a previous byte is lost

due to an overrun. The FSK-FRM Error bit (Status register, bit 2) indicates an

incorrect start- or stop-bit. These frame errors indicate that there are synchronization

problems. The on-chip level detector can be used to detect a carrier loss during FSK

transmission. FSK data can be rejected when the signal level is below the reference

level, this to avoid that noise is interpreted as data (Interrupt register, bit 4 is logic 1).

7.4 Ring or polarity change detector

For ring and polarity change detection two comparators are available in the

PCD3316. The reference level of the comparators is set internally by the reference

voltage generator. The voltage levels on the two polarity comparator inputs, POL0

and POL1, are compared with the reference voltage Vref. If POL0 < Vref or

POL1 > Vref, POL0 and POL1 (Status register, bit 7 and 6) are set respectively and

reset if POL0 > Vref and POL1 < Vref. Every time the POL0 status bit changes from

logic 1 to logic 0, a POL0 interrupt is generated. Every time the POL1 status bit

changes from logic 0 to logic 1, a POL1 interrupt is generated.

The period time of a POL1-POL0-POL1 sequence is available in the Ringer period

generated. The sequence is:

1. Power-on: Ringer period register = 255

2. First POL1 interrupt: Ringer period register = 255

3. First POL1 interrupt after a POL0 interrupt: Ringer period register = new time

4. First POL1 interrupt after more than 255

⁄

2048 s: Ringer period register = 255.

The period is given in multiples of 1

⁄

2048 s. The maximum value is 255.

The POL1-POL0-POL1 sequence is recognized when one or more POL1 interrupts

are generated followed by one or more POL0 interrupts, followed by a POL1 interrupt.

The 32.768 kHz clock is needed for the generation of a polarity interrupt.

7.5 Low battery detection

The low battery voltage detection input (pin LOWBAT) is connected to the positive

input of a comparator. The negative input is connected to the internal reference

voltage. If the voltage on the LOWBAT input pin is less than the reference voltage Vref,

the LOW-BAT Indication (Status register, bit 5) is set. If the LOWBAT input rises

above Vref again, the LOW-BAT Indication is cleared.

Fig 4.

IRQ generation after reading a valid data byte.

handbook, full pagewidth

MBH981

START

IRQ

read by

serial interface

STOP

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