AD7993 datasheet(26/27 Pages) AD

26 / 27 page

AD7994/AD7993

–26–

REV. PrF

PRELIMINARYTECHNICAL DATA

Figure 17. Mode 2 Operation

Figure 18. Mode 2 Sequence Operation

Mode 3 - Automatic Cycle Mode

An automatic conversion cycle can be selected and enabled

by writing a value to the Cycle Timer Register. A conver-

sion cycle interval can be set up on the AD7994/AD7993

by programming the relevant bits in the 3-bit Cycle Timer

Timer register is programmed with any configuration

other than all 0’s, a conversion will take place every X ms,

depending on the configuration of these bits in the Cycle

Timer Register. There are 7 different cycle time intervals

to choose from as shown in Table XIIb. Once the conver-

sion has taken place the part powers down again until the

next conversion occurs. To exit this mode of operation the

user must program the Cycle Timer Register to contain

all 0’s. For cycle interval options see Table XIIb Cycle

Timer Intervals. To select a channel(s) for operation in

the cycle mode set the corresponding channel bit(s), D7 to

D4, of the Configuration Register. If more than one chan-

nel bit is set in the Configuration register the ADC will

automatically cycle through the Channel sequence, start-

ing with the lowest channel and working its way up

through the sequence. Once the sequence is complete the

ADC will start converting on the lowest channel again,

continuing to loop through the sequence until the Cycle

timer register contents are set to all 0’s. This mode is

useful for monitoring signals, e.g. battery voltage, tem-

perature etc, interrupting only when the limits are vio-

lated.

SCL

7-BIT ADDRESS

WA COMMAND/ADDRESS POINT BYTE A

SDA

7-BIT ADDRESS

FIRST DATA BYTE (MSBs)

SECOND DATA BYTE (LSBs)

SDA

SCL

Sr/

ACK BY

AD7994/3

ACK BY

AD7994/3

ACK BY

AD7994/3R

ACK BY

MASTER

NACK BY

MASTER

SCL

7-BIT ADDRESS

WA COMMAND/ADDRESS POINT BYTE A

SDA

FIRST DATA BYTE (MSBs)

SECOND DATA BYTE (LSBs)

7-BIT ADDRESS

SDA

SCL

ACK BY

AD7994/3

ACK BY

AD7994/3

ACK BY

AD7994/3

ACK BY

MASTER

FIRST DATA BYTE (MSBs)

SECOND DATA BYTE (LSBs)

ACK BY

MASTER

ACK BY

MASTER

RESULT FROM CH1

RESULT FROM CH2

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