CAP1298 datasheet(38/68 Pages) MICROCHIP

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CAP1298

DS00001571B-page 38

 2013-2015 Microchip Technology Inc.

APPLICATION NOTE: The programmed sensing cycle time (CYCLE_TIME[1:0]) is only maintained if the actual time

to take the samples is less than the programmed cycle time. The AVG[2:0] bits will take

priority, so the sensing cycle time will be extended as necessary to accommodate the

number of samples to be measured.

5.10.1

CALIBRATION ACTIVATE AND STATUS REGISTER

The Calibration Activate and Status Register serves a dual function:

It forces the selected sensor inputs to be calibrated, affecting both the analog and digital blocks (see Section 4.4,

"Sensor Input Calibration"). When one or more bits are set, the device performs the calibration routine on the

corresponding sensor inputs. When the analog calibration routine is finished, the CALX[9:0] bits are updated (see

Section 5.28, "Sensor Input Calibration Registers"). If the analog calibration routine completed successfully for a

sensor input, the corresponding bit is automatically cleared.

APPLICATION NOTE: In the case above, bits can be set by host or are automatically set by the device whenever

a sensor input is newly enabled (such as coming out of Deep Sleep, after power-on reset,

when a bit is set in the Sensor Enable Channel Enable register (21h) and the device is in

the Active state, or when a bit is set in the Standby Channel Enable Register (40h) and the

device is in the Standby state).

It serves as an indicator of an analog calibration failure. If any of the bits could not be cleared, the ACAL_FAIL

bit is set (see Section 5.2, "Status Registers"). A bit will fail to clear if a noise bit is set or if the calibration value

is at the maximum or minimum value.

APPLICATION NOTE: In the case above, do not check the Calibration Activate and Status bits for failures unless

the ACAL_FAIL bit is set. In addition, if a sensor input is newly enabled, do not check the

Calibration Activate and Status bits until time has elapsed to complete calibration on the

sensor input. Otherwise, the ACAL_FAIL bit may be set for one sensor input, but the newly

enabled sensor input may still be set to ‘1’ in the Calibration Activate and Status, not because

it failed, but because it has not been calibrated yet.

For all bits in this register:

• ‘0’ - No action needed.

• ‘1’ - Writing a ‘1’, forces a calibration on the corresponding sensor input. If the ACAL_FAIL flag is set and this bit is

set (see application note above), the sensor input could not complete analog calibration.

Bit 7 - CS8_CAL - Bit for CS8 input.

Bit 6 - CS7_CAL - Bit for CS7 input.

Bit 5 - CS6_CAL - Bit for CS6 input.

Bit 4 - CS5_CAL - Bit for CS5 input.

Bit 3 - CS4_CAL - Bit for CS4 input.

Bit 2 - CS3_CAL - Bit for CS3 input.

Bit 1 - CS2_CAL - Bit for CS2 input.

Bit 0 - CS1_CAL - Bit for CS1 input.

APPLICATION NOTE: Writing a ‘0’ to clear a ‘1’ may cause a planned calibration to be skipped, if the calibration

routine had not reached the sensor input yet.

TABLE 5-22:

CALIBRATION ACTIVATE AND STATUS REGISTER

Addr

R/W

B5B4

B3B2B1

Default

26h

R/W

Calibration

Activate

and Status

CS8_

CAL

CS7_

CAL

CS6_

CAL

CS5_

CAL

CS4_

CAL

CS3_

CAL

CS2_

CAL

CS1_

CAL

00h

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