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WM8321

PD, February 2012, Rev 4.0

18.3 AUXADC READBACK

Measured data from the AUXADC is read via the AuxADC Data Register (R16429), which contains

two fields. The AUXADC Data Source is indicated in the AUX_DATA_SRC field; the associated

measurement data is contained in the AUX_DATA field.

Reading from the AuxADC Data Register returns a 12-bit code which represents the most recent

AUXADC measurement on the associated channel. It should be noted that every time an AUXADC

measurement is written to the AuxADC Data Register, the previous data is overwritten - the host

processor should ensure that data is read from this register before it is overwritten. The AUXADC

interrupts can be used to indicate when new data is available - see Section 18.5.

The 12-bit AUX_DATA field can be equated to the actual voltage (or temperature) according to the

following equations, where AUX_DATA is regarded as an unsigned integer:

The maximum voltage that can be measured on the input pins GPIO10, GPIO11 and GPIO12 is

determined by the power domain associated with each; this is selectable on a pin by pin basis using

the GPn_PWR_DOM register bits described in Section 21.3. The input voltage at the GPIO pin must

not exceed the voltage of the respective power domain (ie. DBVDD or PVDD).

In a typical application, it is anticipated that the AUXADC Interrupts would be used to control the

AUXADC readback - the host processor should read the AUXADC Data Register in response to the

AUXADC Interrupt event. See Section 18.5 for details of AUXADC Interrupts. In Automatic AUXADC

mode, the processor should complete this action before the next measurement occurs, in order to

avoid losing any AUXADC samples. In Manual conversion mode, the interrupt signal provides

confirmation that the commanded measurement has been completed.

The control fields associated with initiating AUXADC readback are defined in Table 46.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R16429

(402Dh)

AuxADC Data

15:12

AUX_DATA_SRC

[3:0]

000

AUXADC Data Source

1 = GPIO10

2 = GPIO11

3 = GPIO12

5 = Chip Temperature

7 = PVDD voltage

All other values are Reserved

11:0

AUX_DATA [11:0]

000h

AUXADC Measurement Data

Voltage (mV) = AUX_DATA x 1.465

ChipTemp (

C) = (498 - AUX_DATA)

/ 1.09

Table 46 AUXADC Readback

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