Silan

Semiconductors

SC9257

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.0

2001.10.18

13

2.

Prescaler and programmable counter circuit configuration

(1) Pulse swallow mode circuit configuration

1/2

2 modulus

prescaler

4bit swallow counter

12bit programmable counter

FM,MODE

Preset

To phase

comparator

PSC

P4-P15

P0-P3

FM

L

FM

H

Prescaler section

HF

Fig.3

This circuit consists of a 2 modulus prescaler, a 4 bit swallow counter and a 12bit programmable counter.

During FM

(2) Direct dividing method circuit configuration

AM

IN

12bit program counter

Amp

P4-P15

To phase comparator

Preset

Fig.4

With the direct dividing mode, the prescaler section is bypassed and the 12bit programmable counter is used.

(3) Both FM

low amplitude.

General-purpose counter

The general-purpose counter is a 20bit counter. It has such uses as counting AM/FM band intermediate

frequencies (IF) and detecting auto-stop signals during auto-search tuning. It also features a cycle measurement

function for such uses as measuring low-frequency pilot signal cycles.

1. General-purpose counter control bits

(1) Bits G0 and G1 … Used for selecting the general-purpose counter gate time.