AD6636BBCZ1 datasheet(48/72 Pages) AD

48 / 72 page

AD6636

Rev. 0 | Page 48 of 72

Hop with Soft Sync

The AD6636 can synchronize a change in NCO frequency

and/or phase offset of multiple channels or chips under

microprocessor control. The NCO hop hold-off counter, in

conjunction with the soft hop enable bit and the channel enable

bits, enables this synchronization.

To synchronize the hop of multiple channels via microprocessor

control:

Write the NCO frequency register(s) or phase offset

Write the NCO frequency hold-off counter(s) to the

appropriate value (greater than 1 and less than 2^16).

Write the soft hop synchronization enable bit and the

corresponding soft sync channel enable bits high in the soft

synchronization configuration register. This starts the

countdown by the frequency hold-off counter. When the

count reaches 1, the new frequency and/or phase offset is

loaded into the NCO.

Hop with Pin Sync

Four sync pins (0, 1, 2 and 3) provide very accurate synchro-

nization among channels. Each channel can be programmed to

look at any of the four sync pins.

To control the hop of channel NCO frequencies:

Write the NCO frequency register(s) or phase offset

Write the NCO frequency hold-off counter(s) to the

appropriate value (greater than 1 and less than 216).

Program the channel NCO control registers to monitor the

appropriate SYNC pins.

Write the hop synchronization enable bit and SYNC pin

enable bits high in the pin synchronization configuration

hold-off counter. When the reaches 1, the new frequency

and/or phase offset is loaded into the NCO.

SERIAL PORT CONTROL

The AD6636 serial port allows the programming and readback

of all control registers and coefficient memory, serially, in 1-byte

words. The serial port can work in two modes, selected using

the MODE pin (SPI = 0, SPORT = 1). In both SPI and SPORT

modes, the AD6636 is compatible with Blackfin, TigerSHARC,

and other DSPs. The serial port and microport share some of

the I/O pins; therefore, only one of these ports is operational at

a time.

The selection between the serial port and microport modes is

made using the SMODE pin (serial port = 1, microport = 0).

The serial port has a chip select pin (active low signal), which

should be pulled low for any operation on the serial port. Serial

data can be shifted into the part or out of the part as either MSB

first or LSB first using the MSBFIRST pin (1 = MSB first, 0 =

LSB first).

Hardware Interface

The pins listed in Table 25 comprise the physical interface

between the user’s programming device and the AD6636 serial

port. All serial pins are inputs except for SDO, which is an open-

drain output and should be pulled high by an external pull-up

resistor (typical value of 1 kΩ).

Table 25. Serial Port Pin Names and Functions

Pin Name

Function

SCLK

Serial clock in both SPI and SPORT modes. Serial data is clocked in on the rising edge of SCLK.

MSBFIRST

Indicates whether the first bit shifted in or out of the serial port is the MSB (1) or LSB (0) of the data word.

STFS

Serial transmit frame sync in SPORT mode; ignored in SPI mode.

SRFS

Serial receive frame sync in SPORT mode; ignored in SPI mode.

SDI

Serial data input in both modes.

SDO

Serial data output in both modes.

SCS

Active low serial chip select in both modes. Setting this pin high holds the serial port in reset. It should be pulled low for

any read/write operation on serial port.

SMODE

Serial mode. Partis programmed through the serial port when this pin is Logic 1.

MODE

Mode pin. Selects between SPI (0) and SPORT (1) modes.

AD6636BBCZ1 Datasheet(PDF) 48 Page - Analog Devices

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