Register 10: ADC Sample Phase Control (ADCSPC), offset 0x024
The
ADC Sample Phase Control (ADCSPC)
register is used to insert a delay in ADC module
sampling. This feature can be used with the
SYNCWAIT
and
GSYNC
bit in the
ADCPSSI
register to
provide concurrent sampling of two different signals by two different ADC modules or skewed
sampling of two ADC modules to increase the effective sampling rate. For concurrent sampling, the
PHASE
field of each ADC module must be the same and the sample and hold times (
TSHn
) for the
matching sample steps of each ADC must be the same. For example, both ADC0 and ADC1 would
program PHASE = 0x0 in the
ADCSPC
register and might both have the following configuration for
their
ADCSSTSH0
register:
■
TSH7
=0x4
■
TSH6
=0x2
■
TSH5
=0x2
■
TSH4
=0x8
■
TSH3
=0x6
■
TSH2
=0x2
■
TSH1
=0x4
■
TSH0
=0x2
For skewed sampling with a consistent phase lag, the
TSHn
field in the
ADCSSTSHn
register must
be the same for all sample steps of an ADC and for both ADC Modules. The desired lag can be
calculated by adding the sample and hold time (
TSHn
) to the twelve clock conversion time to
determine the total number of clocks in a sample period. For example to create a 180.0° phase lag,
the
PHASE
of the lagging ADC is calculated as:
PHASE = (
TSHn
+ 12)/2, where TSHn is in ADC_Clocks
For situations where a predictable phase lag is not required, sample and hold times (TSHn) of ADC
modules can vary.
Note:
Care should be taken when the
PHASE
field is non-zero, as the resulting delay in sampling
the
AINx
input may result in undesirable system consequences. The time from ADC trigger
to sample is increased and could make the response time longer than anticipated. The
added latency could have ramifications in the system design. Designers should carefully
consider the impact of this delay.
1101
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller