SC9257 Datasheet, PDF (11/28 Pages) Silan Microelectronics Joint-stock – PLL FOR DTS

Silan
Semiconductors
SC9257
Reference counter (Reference frequency divider)
The reference counter section consists of a crystal oscillator and a counter.
A crystal oscillator frequency of 3.6MHZ, 7.2MHZ or 10.8MHZ can be selected .A maximum of 15 reference
frequencies can be generated.
1. Setting reference frequency
The reference frequency is set using bits R0~R3.
LSB
Address D0H
R0 R1 R2 R3
MSB
R0 R1 R2 R3
REFERENCE
FREQUENCY
0000
0.5 KHz
1000
1 KHz
0100
2.5 KHz
1100
3 KHz
0010
3.125 KHz
1 0 1 0 *3.90654 KHz
0110
5 KHz
1110
6.25 KHz
R0 R1 R2 R3
REFERENCE
FREQUENCY
0001
*7.8125 KHz
1001
9 KHz
0101
10 KHz
1101
12.5 KHz
0011
25 KHz
1011
50 KHz
0111
100 KHz
1 1 1 1 Standby mode (*1)
(Note 1) Reference frequencies marked with an asterisk “*”can only be generated with a 4.5MHZ crystal oscillator.
(Note 2) (*1)Standby mode
Standby mode occurs when bits R0,R1,R2,and R3 are all set to “1”.In standby mode, the programmable
counter stops, and FM, AM and IFIN(when selected IFIN) are set to “amp off” state (pins at “L” level). This
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-9) and output ports (OT1~OT4) can be controlled and the
crystal oscillator can be turned on and off.
(Note 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.
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.0
11
2001.10.18