Datasheet

AD7294 Data Sheet

Rev. H | Page 40 of 48

AUTOCYCLE MODE

The AD7294 can be configured to convert continuously on a

programmable sequence of channels making it the ideal mode

of operation for system monitoring. These conversions take

place in the background approximately every 50 µs, and are

transparent to the master. Typically, this mode is used to

automatically monitor a selection of channels with either the

limit registers programmed to signal an out-of-range condition

via the alert function or the minimum/maximum recorders

tracking the variation over time of a particular channel. Reads

and writes can be performed at any time (the ADC Result

On power up, this mode is disabled. To enable this mode, write

to Bit D12 in the configuration register (0x09) and select the

desired channels for conversion in the channel sequence

If a command mode conversion is required while the autocycle

mode is active, it is necessary to disable the autocycle mode before

proceeding to the command mode. This is achieved either by clear-

ing Bit D12 of the configuration register or by writing 0x00 to the

channel sequence register. When the command mode conversion is

complete, the user must exit command mode by issuing a stop

condition before reenabling autocycle mode.

When switching out of autocycle mode to command mode,

the temperature sensor must be given sufficient time to settle

and complete a new temperature integration cycle. Therefore,

temperature sensor conversions performed within the first

500 ms after switching from autocycle mode to command mode

may result in false temperature high and low alarms being

triggered. It is recommended to disable temperature sensor

alarms for the first 500 ms after mode switching by writing

0x400 to the DATA

LOW

SENSE

x register and 0x3FF to the

DATA

HIGH

SENSE

x. The temperature sensor alerts should

be reconfigured to the desired alarm level once the 500 ms has

elapsed. Alternatively, temperature alerts triggered during the

first 500 ms after mode switching should be ignored.