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ADC Registers
738
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Analog-to-Digital Converter (ADC)
10.5.10 ADCSPC Register (Offset = 0x24) [reset = 0x0]
ADC Sample Phase Control (ADCSPC)
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 degree 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.
ADCSPC is shown in
and described in
Return to
Figure 10-24. ADCSPC Register
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RESERVED
R-0x0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RESERVED
PHASE
R-0x0
R/W-0x0