AS39513 datasheet(87/108 Pages) AMSCO

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ams Datasheet

Page 87

[v1-10] 2018-Apr-25

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AS39513 − Detailed Description

The do measurement command initiates a specific

measurement outside the normal logging loop. The command

reply will wait for the ADC conversion to complete. The ADC

algorithm will use a mode that always takes the same amount

of time for a given oscillator clock frequency, independent of

the conversion value. The format of the Meas parameter is

below.

Measurement Parameter Format

where:

DOMEAS[1:0] – Measurement type to initiate.

0 = Do a temperature measurement.

1 = Do a battery level measurement.

2 = Do a sensor measurement.

3 = Reserved; do not use.

Note the Do Measurement -Temperature command results in

some self heating of the chip due to the presence of the RF field

from the reader, so temperature accuracy cannot be

guaranteed with this command. Temperature sensing is

intended to be carried out in logging mode.

The do measurement command returns the 10-bit ADC result,

formatted in a two-byte word as shown below,

ADC Result Format

where:

ADC_RES[9:0] – ADC measurement result.

An example of a “good” reply is 0x0001AC (where 00 => no error

in RFLAGs, and 01AC => ADC data). An ADC error reply is 01A3

(where 01 => error indicated in RFLAGS, A3 => ADC error code)

Bit

Meas

DOMEAS[1:0]

Bit

ADC

000

ADC_RES[9:0]

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