3

FN2810.9

April 25, 2007

Pin Description

NAME

TYPE

DESCRIPTION

+5V power supply pin.

GND

Ground

P0-1

I

Phase modulation inputs (become active after a pipeline delay of four clocks). A phase shift of 0°, 90°,

180°, or 270° can be selected as shown in Table 1.

CLK

I

NCO clock. (CMOS level)

SCLK

I

This pin clocks the frequency control shift register.

SEL_L/M

I

A high on this input selects the least significant 32 bits of the 64-bit frequency register as the input to

the phase accumulator; a low selects the most significant 32 bits.

SFTEN

I

The active low input enables the shifting of the frequency register.

MSB/LSB

I

This input selects the shift direction of the frequency register. A low on this input shifts in the data LSB

first; a high shifts in the data MSB first.

ENPHAC

I

This pin, when low, enables the clocking of the Phase Accumulator. This input has a pipeline delay of

four clocks.

SD

I

Data on this pin is shifted into the frequency register by the rising edge of SCLK when SFTEN is low.

TXFR

I

This active low input is clocked onto the chip by CLK and becomes active after a pipeline delay of four

clocks. When low, the frequency control word selected by SEL_L/M is transferred from the frequency

register to the phase accumulator’s input register.

LOAD

I

This input becomes active after a pipeline delay of five clocks. When low, the feedback in the phase

accumulator is zeroed.

OUT0-11

O

Output data. OUT0 is LSB. Unsigned.

All inputs are TTL level, with the exception of CLK.

Overline designates active low signals.

HSP45102