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1.8 ADC Calibration

ADC Calibration

Recommendations and caution on sequencer override feature:

• After reset, SEQ_OVRD bit will be 0; therefore the sequencer override feature remains disabled.

• When SEQ _OVRD bit is set for all nonzero values of MAX_CONVn, the related interrupt flag bit will

be set for every MAX_CONVn count of result register update.

• For example, if ADCMAXCONV is set to 3, then the interrupt flag for the selected sequencer will be set

every four result register updates. The wraparound always occurs at the end of the sequencer (i.e.,

after ADCRESULT15 register update in cascaded sequencer mode).

• This will be functional in conversions using SEQ1, SEQ2, and cascaded sequencers using SEQ1.

• It is recommended that this feature not be enabled/controlled dynamically within the program. Always

enable this feature during the ADC module initialization.

• In continuous-conversion mode with sequencer changes, the ADC channel address uses the preset

values in CONVxx registers. If continuous conversions of the same channel are needed then all the

CONVxx registers should have the same channel address.

• In continuous-conversion mode, if a sequencer reset is needed: set CONT_RUN bit to 0, wait 2 cycles

in the ADC Clock domain, then reset the sequencer. CONT_RUN can then be set back to 1.

• For example, to get 16 contiguous samples for the ADCINA0 channel using the sequencer override

feature, all 16 CONVxx registers should be set to 0x0000.

The ADC_cal() routine is programmed into TI reserved OTP memory by the factory. The boot ROM

automatically calls the ADC_cal() routine to initialize the ADCREFSEL and ADCOFFTRIM registers with

device specific calibration data. During normal operation, this process occurs automatically and no action

is required by the user.

If the boot ROM is bypassed by Code Composer Studio during the development process, then

ADCREFSEL and ADCOFFTRIM must be initialized by the application. For working examples, see the

ADC initialization in the C2833x C/C++ Header Files and Peripheral Examples (SPRC530 ).

The next two sections describe different methods for calling the ADC_Cal() routine.

Note: FAILURE TO INITIALIZE THESE REGISTERS WILL CAUSE THE ADC TO FUNCTION

OUT OF SPECIFICATION.

Because TI reserved OTP memory is secure, the ADC_Cal() routine must be called from

secure memory or called from non-secure memory after the Code Security Module is

unlocked. If the system is reset or the ADC module is reset using Bit 14 (RESET) from the

ADC Control Register 1, the routine must be repeated.

Analog-to-Digital Converter (ADC)28 SPRU812A – September 2007 – Revised October 2007

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ADC 320F Spezifikationen Seite 28