AS39513 datasheet(24/108 Pages) AMSCO

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[v1-10] 2018-Apr-25

AS39513 − Detailed Description

Status Parameters: As a last step in the logging operation, the

measurement count, MEASCNT, is incremented.

If update counts SKIP16 = 0 or MEASCNT[3:0] = 4’b1111, then

MEASCNT, the status bits ACTIVE, EEFULL, OVWRT, ADCERR,

LOWBAT, and OVLIM, and the ending measurement pointer

MEASPTR are written into EEPROM.

Even if no logging occurred (because the limit conditions were

not met or the EEPROM was full), the measurement count

MEASCNT is still incremented and written into EEPROM (still

using the SKIP16 option to only write once every 16

measurements). The measurement counter MEASCNT clips at

16’hFFFF so that it does not wraparound to 0. The measurement

pointer MEASPTR is only updated if data was logged to the

EEPROM; it always points to just after the end of the data that

was actually written to EEPROM.

Logging Arbitration: In the condition that another enabled

logging event occurs before the logging of the current event is

complete, the next logging event will be queued and will

commence at the completion of the current logging operation.

If an RFID or SPI command request occurs during logging, the

command is ignored in order to prevent conflicts in EEPROM

access.

Power Modes

The controller modes described above also control which of the

sensor blocks are enabled.

If the controller is in any of the COMMAND modes, the LOGGING

mode or the RESET initialization, there is a high-speed

(fSYS=1.92 MHz) ring oscillator that is enabled to clock the

controller logic and the EEPROM.

In the LOGGING mode, there are three additional power modes.

Battery check mode (bchk_md) enables all the sensor circuits

needed to do the coarse battery check, which is basically

everything in the sensor system except the ADC. Measure mode

(meas_md) enables basically everything in the sensor system

except the battery check circuit; this mode is used for

temperature and external sensor measurements. Battery

voltage mode (both bchk_md and meas_md enabled) is used

to measure the battery voltage.

If the AS39513 is not in one of the modes requiring the ring

oscillator, the ring oscillator is disabled and the lowpow signal

is asserted. This signal causes the power switch in the AFE to

switch to an unregulated supply for the logic, further reducing

the power consumption. The only circuits that are operational

in this low power mode that would draw current from the

external battery are the real time oscillator (if OSCEN = 1) and

the external interrupt comparator (if EIEN = 1).

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