WM8321 Datasheet, PDF (99/253 Pages) Wolfson Microelectronics plc – Processor Power Management Subsystem

Production Data
WM8321
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
R16429
(402Dh)
AuxADC Data
BIT
15:12
LABEL
AUX_DATA_SRC
[3:0]
11:0 AUX_DATA [11:0]
Table 46 AUXADC Readback
DEFAULT
000
000h
DESCRIPTION
AUXADC Data Source
1 = GPIO10
2 = GPIO11
3 = GPIO12
5 = Chip Temperature
7 = PVDD voltage
All other values are Reserved
AUXADC Measurement Data
Voltage (mV) = AUX_DATA x 1.465
ChipTemp (C) = (498 - AUX_DATA)
/ 1.09
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PD, February 2012, Rev 4.0
99