AD4080BBCZ datasheet(56/95 Pages) AD

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Data Sheet

AD4080

DIGITAL FEATURES

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Rev. 0 | 56 of 95

FIFO Mode Selection and Configuration

There are four distinct modes in which the data FIFO of the AD4080

can be configured. The active mode is selected by setting the

FIFO_MODE bits in the general configuration register (see the

General Configuration Register section, Address 0x1C). By default,

the FIFO is disabled (FIFO_MODE = 00). The modes are designed

to fit the use case requirements of different applications., Table 27

provides details about each FIFO mode and their applicable use

cases.

Table 27. FIFO Configuration Modes (FIFO_MODE)

FIFO_MODE Bit

Value

FIFO Mode

Description

Use Case

FIFO disabled

FIFO is not used. This value also resets and rearms the event

trigger.

Continuous convert mode, and FIFO is not in use.

Immediate trigger mode

In this mode, the data capture is initiated immediately after

receipt of the first valid converter result and continues until [N =

WATERMARK] results are loaded into the FIFO memory.

User is interested in burst acquisition(s) of [N

= WATERMARK] results, initiated by setting this

FIFO_MODE, Bits[1:0] value.

Upon read back from the FIFO, FIFO_READ_DONE indicates

when [N = WATERMARK] results are read from the FIFO.

Event trigger capture, read

latest WATERMARK

The data capture into the FIFO memory is initiated by the

user-selected event method. The result counter initiates by

the event, and data captures to the FIFO stop once [N =

WATERMARK] results are captured.

User is interested in burst acquisition(s) of [N =

WATERMARK] results, initiated by an event. Only result

data after the event is of interest.

Upon read back from the FIFO, FIFO_READ_DONE indicates

when [N = WATERMARK] results have been read from the

FIFO.

Event trigger capture mode,

read all FIFO

The data capture immediately initiates after the receipt of the

first valid converter result.

User is interested in burst acquisition(s) of [N =

WATERMARK] results initiated by an event. The full

FIFO contents are read in this mode. In this mode, the

user can read [N = WATERMARK] results after the event

and (16,384 − [N = WATERMARK]) before the event.

Only WATERMARK values that are multiples of four are

valid in this mode.

The FIFO continuously fills until an event is detected. If no

event is detected before the FIFO fills (that is, 16,384 results

are written to memory), the memory continues to fill with the

oldest results discarded on a first in, first out basis.

Upon receipt of the selected event method, a result counter

counts up to [N = WATERMARK]. Data capture stops once the

WATERMARK is reached. In this mode, once the FIFO is filled,

the position in the FIFO memory at which the event occurred

gets automatically stored in the FIFO_WATERMARK register.

The value read back from FIFO_WATERMARK allows the user

to distinguish which of the stored results captured before the

event from those that were captured after the event. Further

details can be seen in the example given in the Event Trigger

Capture Mode, Read All FIFO section.

Upon read back from the FIFO, FIFO_READ_DONE indicates

when 16,384 results are read from the FIFO. The full memory

read back contains [N = WATERMARK] results after the event.

If N in this case is less than 16,384, the remaining contents of

the FIFO contain the conversion results prior to the event.

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