MAX30002 datasheet(39/44 Pages) MAXIM

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BIOZ FIFO Memory (8 Words x 24 Bits)

The BIOZ FIFO memory is a standard circular FIFO

consisting of 8 words, each with 24 bits of information.

The BIOZ FIFO is independently managed by internal

read and write pointers. The read pointer is updated in

response to the 32nd SCLK rising edge in a normal mode

read back transaction and on the (32 + n x 24)th SCLK

rising edge(s) in a burst mode transaction where n = 0 to

up to 31. Once a FIFO sample is marked as read, it can-

not be accessed again.

The write pointer is governed internally. To aide data

management and reduce µC overhead, the device pro-

vides a user-programmable BIOZ FIFO Interrupt Threshold

(BFIT[2:0]) governing the BIOZ Interrupt bit (BINT). This

threshold can be programmed with values from 1 to 8, rep-

resenting the number of unread BIOZ FIFO entries required

before the BINT bit will be asserted, alerting the µC that

there is a significant amount of data in the BIOZ FIFO ready

for read back (see MNGR_INT (0x04) for details).

If the write pointer ever traverses the entire FIFO array

and catches up to the read pointer (due to failure of the

µC to read/maintain FIFO data), a FIFO overflow will

occur and data will be corrupted. The BOVF STATUS

and tag bits will indicate this condition and the FIFO

should be cleared before continuing measurements using

either a SYNCH or FIFO_RST command—note overflow

events will result in the loss of samples and thus timing

information, so these conditions should not occur in well-

designed applications.

Do not read beyond the last valid FIFO word to prevent

possible data corruption.

BIOZ FIFO Data Structure

The data portion of the word contains the 20-bit BIOZ volt-

age information measured at the requested sample rate

in left justified two’s complement format. One bit is set to

0 and the remaining three bits of data hold important data

tagging information (see details in Table 30).

Table 30. BIOZ FIFO BIOZ Data Tags (BTAG[2:0] = D[2:0])

BTAG [2:0]

DESCRIPTION

RECOMMENDED USER ACTION

DATA

VALID

TIME

VALID

000

Valid Sample

Log sample into BIOZ record and increment the time

step. Continue to read data from the BIOZ FIFO.

Yes

001

Over/Under Range Sample

Log sample into BIOZ record and increment the

time step. Determine if the data is valid or a lead off

condition. Continue to read data from the BIOZ FIFO.

Yes

010

Last Valid Sample

(EOF)

Log sample into BIOZ record and increment the time

step. Suspend read of the BIOZ FIFO until more

samples are available.

Yes

011

Last Over/Under Range

Sample (EOF)

Log sample into BIOZ record and increment the

time step. Determine if the data is valid or a lead off

condition. Suspend read of the BIOZ FIFO until more

samples are available.

Yes

10x

Unused

110

FIFO Empty

(exception)

Discard this sample without incrementing the time

base. Suspend read of the BIOZ FIFO until more

samples are available.

111

FIFO Overflow

(exception)

Discard this sample without incrementing the time

base. Issue a FIFO_RST command to clear the FIFOs

or re-SYNCH if necessary. Note the corresponding

halt and resumption in all the FIFOs.

MAX30002

Ultra-Low-Power, Single-Channel Integrated

Bioimpedance (BioZ) AFE

www.maximintegrated.com

Maxim Integrated │ 39

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