AD7710 datasheet(25/28 Pages) AD

25 / 28 page

AD7710

REV. F

–25–

REVERSE

ORDER OF

BITS

START

WRITE DATA FROM

ACCUMULATOR TO

SERIAL BUFFER

BRING

TFS & A0 LOW

LOAD DATA FROM

ADDRESS TO

ACCUMULATOR

CONFIGURE &

INITIALIZE

C/ P

SERIAL PORT

BRING

RFS, TFS & A0 HIGH

BRING

TFS & A0 HIGH

END

Figure 16. Flowchart for Single Write Operation to the

AD7710

AD7710 to 8XC51 Interface

Figure 17 shows an interface between the AD7710 and the

8XC51 microcontroller. The AD7710 is configured for its exter-

nal clocking mode while the 8XC51 is configured in its Mode 0

serial interface mode. The

DRDY line from the AD7710 is

connected to the Port P1.2 input of the 8XC51 so the

DRDY

line is polled by the 8XC51. The

DRDY line can be connected

to the

INT1 input of the 8XC51 if an interrupt driven system is

preferred.

P1.0

P3.0

P3.1

P1.1

P1.2

P1.3

8XC51

AD7710

SDATA

RFS

TFS

MODE

DRDY

SYNC

SCLK

DVDD

Figure 17. AD7710 to 8XC51 Interface

Table VII shows some typical 8XC51 code used for a single 24-

bit read from the output register of the AD7710. Table VIII

shows some typical code for a single write operation to the con-

trol register of the AD7710. The 8XC51 outputs the LSB first

in a write operation while the AD7710 expects the MSB first so

the data to be transmitted has to be rearranged before being

written to the output serial register. Similarly, the AD7710

outputs the MSB first during a read operation while the 8XC51

expects the LSB first. Therefore, the data which is read into the

serial buffer needs to be rearranged before the correct data word

from the AD7710 is available in the accumulator.

Table VII. 8XC51 Code for Reading from the AD7710

MOV SCON,#00010001B;

Configure 8051 for MODE 0

Operation

MOV IE,#00010000B;

Disable All Interrupts

SETB 90H;

Set P1.0, Used as

RFS

SETB 91H;

Set P1.1, Used as

TFS

SETB 93H;

Set P1.3, Used as A0

MOV R1,#003H;

Sets Number of Bytes to Be Read in

A Read Operation

MOV R0,#030H;

Start Address for Where Bytes Will

Be Loaded

MOV R6,#004H;

Use P1.2 as

DRDY

WAIT:

NOP;

MOV A,P1;

Read Port 1

ANL A,R6;

Mask Out All Bits Except

DRDY

JZ READ;

If Zero Read

SJMP WAIT;

Otherwise Keep Polling

READ:

CLR 90H;

Bring

RFS Low

CLR 98H;

Clear Receive Flag

POLL:

JB 98H, READ1

Tests Receive Interrupt Flag

SJMP POLL

READ 1:

MOV A,SBUF;

Read Buffer

RLC A;

Rearrange Data

MOV B.0,C;

Reverse Order of Bits

RLC A; MOV B.1,C; RLC A; MOV B.2,C;

RLC A; MOV B.3,C; RLC A; MOV B.4,C;

RLC A; MOV B.5,C; RLC A; MOV B.6,C;

RLC A; MOV B.7,C;

MOV A,B;

MOV @R0,A;

Write Data to Memory

INC R0;

Increment Memory Location

DEC R1

Decrement Byte Counter

MOV A,R1

JZ END

Jump if Zero

JMP WAIT

Fetch Next Byte

END:

SETB 90H

Bring

RFS High

FIN:

SJMP FIN

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