Functional Description

The simplified block diagram below shows the 22-bit data register, two 15-bit R Counters and the 15- and 18-bit N Counters (in-

termediate latches are not shown). The data stream is clocked (on the rising edge of Clock) into the DATA register, MSB first. The

data stored in the shift register is loaded into one of 4 appropriate latches on the rising edge of LE. The last two bits are the Con-

trol Bits. The DATA is transferred into the counters as follows:

Control Bits

DATA Location

C1

C2

0

0

IF R Counter

0

1

RF R Counter

1

0

IF N Counter

1

1

RF N Counter

PROGRAMMABLE REFERENCE DIVIDERS (IF AND RF R COUNTERS)

If the Control Bits are 00 or 01 (00 for IF and 01 for RF) data is transferred from the 22-bit shift register into a latch which sets

the 15-bit R Counter. Serial data format is shown below.

15-BIT PROGRAMMABLE REFERENCE DIVIDER RATIO (R COUNTER)

Divide

RRRRRRRRRRRRRRR

Ratio

15 14 13 12 11 10

987654321

3

000000000000011

4

000000000000100

•

•••••••••••••••

32767

111111111111111

Notes:

Divide ratios less than 3 are prohibited.

Divide ratio: 3 to 32767

R1 to R15: These bits select the divide ratio of the programmable reference divider.

Data is shifted in MSB first.

DS012806-6

DS012806-7

www.national.com

12