AD7853_15 datasheet(28/34 Pages) AD

28 / 34 page

REV. B

–28–

AD7853/AD7853L

Writing to the AD7853/AD7853L

For accessing the on-chip registers it is necessary to write to the

part. To enable Serial Interface Mode 1, the user must also

write to the part. Figure 41 through 43 outline flowcharts of

how to configure the AD7853/AD7853L for each of the differ-

ent serial interface modes. The continuous loops on all diagrams

indicate the sequence for more than one conversion. The options

of using a hardware (pulsing the

CONVST pin) or software

(setting the CONVST bit to 1) conversion start, and reading/

writing during or after conversion are shown in Figures 41 and

42. If the

CONVST pin is never used then it should be tied to

DVDD permanently. Where reference is made to the BUSY bit

equal to a Logic 0, to indicate the end of conversion, the user in

this case would poll the BUSY bit in the status register.

Interface Modes 2 and 3 Configuration

Figure 41 shows the flowchart for configuring the part in Inter-

face Modes 2 and 3. For these interface modes, the read and

write operations take place simultaneously via the serial port.

Writing all 0s ensures that no valid data is written to any of the

registers. When using the software conversion start and transfer-

ring data during conversion, Note must be obeyed.

SERIAL

INTERFACE

MODE

POWER-ON, APPLY CLKIN SIGNAL,

WAIT FOR AUTOMATIC CALIBRATION

YES

START

WAIT FOR BUSY SIGNAL TO GO

LOW OR WAIT FOR BUSY BIT = 0

PULSE

CONVST PIN

TRANSFER

DATA

DURING

CONVERSION

APPLY

SYNC (IF REQUIRED), SCLK, READ

CURRENT CONVERSION RESULT ON DOUT PIN,

AND WRITE ALL 0s ON DIN PIN

WAIT FOR BUSY SIGNAL TO GO LOW

OR WAIT FOR BUSY BIT = 0

APPLY

SYNC (IF REQUIRED), SCLK, WRITE TO CONTROL

CONVERSION RESULT ON DOUT PIN

2, 3

INITIATE

CONVERSION

SOFTWARE

WAIT APPROXIMATLY 200ns

AFTER

CONVST RISING EDGE

APPLY

SYNC (IF REQUIRED),

SCLK, READ PREVIOUS CONVERSION

RESULT ON DOUT PIN,

AND WRITE ALL 0s ON DIN PIN

YES

TRANSFER

DATA DURING

CONVERSION

APPLY

SYNC (IF REQUIRED), SCLK, WRITE TO CONTROL

CONVERSION RESULT ON DOUT PIN (SEE NOTE)

YES

NOTE:

WHEN USING THE SOFTWARE CONVERSION START AND TRANSFERRING

DATA DURING CONVERSION THE USER MUST ENSURE THE CONTROL

BUSY. THE FALLING EDGE OF BUSY RESETS THE CONVST BIT TO 0 AND

ONLY AFTER THIS TIME CAN IT BE REPROGRAMMED TO 1 TO START THE

NEXT CONVERSION.

Figure 41. Flowchart for Setting Up, Reading and Writing in Interface Modes 2 and 3

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