Silan

Semiconductors

SC9256

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.0

2002.01.30.

10

Note: 1. Reference frequencies marked with an asterisk “*”can only be generated with a 4.5MHZ crystal oscillator.

2. (*1)Standby mode

Standby mode occurs when bits R0,R1,R2,and R3 are all set to “1”.In standby mode, the programmable

saves current consumption when the radio is turned off. The DO pins become high impedance during

standby mode.

During standby mode, the I/O ports (I/O-5~I/O-6) and output ports (OT1~OT4) can be controlled and the

crystal oscillator can be turned on and off.

3.The system is set to standby mode when power is turned on. At this time, the crystal oscillator is not

oscillating and the I/O ports are set to input mode.

Programmable counter

The programmable counter section consists of a 1/2 prescaler, a 2 modulus prescaler and a 4bit +12bit

programmable binary counter.

1. Setting programmable counter

16 bits of divisor data and 2 bits, which indicate the dividing mode, are set in the programmable counter.

(1) Setting dividing mode

The FM and MODE bits are used to select the input pin and the dividing mode (pulses wallow mode or

direct dividing mode). There are 4 possible choices, shown in the table below .Select one based on the

frequency band used.

LSB

MSB

Address D0H

FM MODE

MODE FM MODE

LF

HF

0

0

1

1

0

1

0

1

DIVIDING MODE

Direct dividing mode

Pulse swallow mode

1/2 + pulse swallow

mode

TYPICAL

RECEIVING BAND

LW,MW,SWL

SWH

FM

FM

INPUT FREQUENCY

RANGE

0.5 ~ 20MHz

1~ 40MHz

30 ~ 130MHz

30 ~ 150MHz

30 ~ 130MHz

INPUT

PIN

FREQUENCY

n

2n

(2)

Setting divisor

The divisor for the programmable counter is set as binary data in bits P0~P15.

• Pulse swallow mode (16 bits)

LSB

MSB

Address D0H

P0

P1

P2

P3

P4

P5

P6

P7

P8

P9 P10 P11 P12 P13 P14 P15

Divisor setting range (pulse swallow mode):n=210H~FFFH (528~65535)

(Note) With the 1/2+pulse swallow mode, the actual divisor is twice the programmed value.