AD6652PCB datasheet(72/76 Pages) AD

72 / 76 page

AD6652

Rev. 0 | Page 72 of 76

ory

R0 at Address (000). When a write to DR0 is

detected, the internal microprocessor port state machine then

moves the data in DR2–DR0 to the internal address pointed to

by the address in the channel address register (CAR) and access

control register (ACR).

ite Pseudocode

void write_micro(ext_address, int data);

main();

{

/* This code shows the programming of the NCO

phase offset register using the write_micro

function as defined above. The variable address is

the External Address A[2:0] and data is the value

to be placed in the external interface register.

Internal Address = 0x087

// holding registers for NCO phase byte wide

access data

int d1, d0;

// NCO frequency word (16 bits wide)

NCO_PHASE = 0xCBEF;

// write ACR

write_micro(7, 0x03 );

// write CAR

write_micro(6, 0x87);

// write DR1 with D[15:8]

d1 = (NCO_PHASE & 0xFF00) >> 8;

write_micro(1, d1);

// write DR0 with D[7:0]

// On this write all data is transferred to the

internal address

d0 = NCO_FREQ & 0xFF;

write_micro(0, d0);

} // end of main

Internal Read Access

A read is performed by first writing the channel address register

(CAR) and ACR as with a write. The data registers (DR2–DR0)

are then read in the reverse order that they were written. First,

the least significant byte of the data (D[7:0]) is read from DR0.

On this transaction, the high bytes of the data are moved from

e internal address pointed to by the CAR and ACR into the

remaining data registers (DR2–DR1). This data can then be

read from the data registers using the appropriate 3-bit

addresses. The number of data registers used depends solely on

the amount of data to be read or written. Any unused bit in a

data register should be masked out for a read.

Read Pseudocode

int read_micro(ext_address);

main();

{

/* This code shows the reading of the first RCF

coefficient using the read_micro function as

defined above. The variable address is the

External Address A[2..0].

Internal Address = 0x000

// holding registers for the coefficient

int d2, d1, d0;

// coefficient (20-bits wide)

long coefficient;

// write ACR

write_micro(7, 0x00 );

// write CAR

write_micro(6, 0x00);

/* read D[7:0] from DR0, All data is moved from

the internal registers to the interface registers

on this access */

d0 = read_micro(0) & 0xFF;

// read D[15:8] from DR1

d1 = read_micro(1) & 0xFF;

// read D[23:16] from DR2

d2 = read_micro(2) & 0x0F;

coefficient = d0 + (d1 << 8) + (d2 << 16);

} // end of main

Internal Write Access

Up to 20 bits of data (as needed) can be written by the following

process. Any high order bytes that are needed are written to th

corresponding data registers defined in the external mem

map 3-bit address space. The least significant byte is then

written to D

AD6652PCB 数据表(PDF) 72 Page - Analog Devices

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