AD7993 datasheet(30/32 Pages) AD

30 / 32 page

AD7993/AD7994

Rev. 0 | Page 30 of 32

SECOND DATA BYTE

(LSBs)

FIRST DATA BYTE

(MSBs)

COMMAND/ADDRESS

POINT BYTE

7-BIT ADDRESS

SDA

SCL

SDA

SCL

Sr/P

ACK BY

AD7993/AD7994

ACK BY

AD7993/AD7994

ACK BY

MASTER

NACK BY

MASTER

ACK BY

AD7993/AD7994

Figure 33. Mode 2 Operation

SCL

7-BIT ADDRESS

COMMAND/ADDRESS

POINT BYTE

SDA

FIRST DATA BYTE

(MSBs)

SECOND DATA BYTE

(LSBs)

FIRST DATA BYTE

(MSBs)

SECOND DATA BYTE

(LSBs)

7-BIT ADDRESS

SDA

SCL

ACK BY

AD7993/AD7994

ACK BY

AD7993/AD7994

ACK BY

MASTER

ACK BY

MASTER

ACK BY

MASTER

ACK BY

AD7993/AD7994

RESULT FROM CH1

RESULT FROM CH2

A/A

Figure 34. Mode 2 Sequence Operation

MODE 3—AUTOMATIC CYCLE INTERVAL MODE

An automatic conversion cycle can be selected and enabled by

writing a value to the cycle timer register. A conversion cycle

interval can be set up on the AD7993/AD7994 by programming

the relevant bits in the 8-bit cycle timer register, as decoded in

Table 25. Only the 3 LSB are used; the 5 MSB should contain 0s.

When the 3 LSB of the register are programmed with any

configuration other than all 0s, a conversion takes place every

X ms; the cycle interval, X, depends on the configuration of

these three bits in the cycle timer register. There are seven

different cycle time intervals to choose from, as shown in

Table 25. Once the conversion takes place, the part powers

down again until the next conversion. To exit this mode of

operation, the user must program the 3 LSB of the cycle timer

the cycle mode, set the corresponding channel bit(s), D7 to D4,

of the configuration register. If more than one channel bit is set

in the configuration register, the ADC automatically cycles

through the channel sequence starting with the lowest channel

and working its way up through the sequence. Once the

sequence is complete, the ADC starts converting on the lowest

channel again, continuing to loop through the sequence until

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

is useful for monitoring signals such as battery voltage, and

temperature, alerting only when the limits are violated.

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