TM4C1294NCZAD Datasheet, PDF (1065/1914 Pages) Texas Instruments – Tiva Microcontroller

Tiva^™ TM4C1294NCZAD Microcontroller
15.3.1
15.3.2
Sample Sequencers
The sampling control and data capture is handled by the sample sequencers. All of the sequencers
are identical in implementation except for the number of samples that can be captured and the depth
of the FIFO. Table 15-2 on page 1065 shows the maximum number of samples that each sequencer
can capture and its corresponding FIFO depth. Each sample that is captured is stored in the FIFO.
In this implementation, each FIFO entry is a 32-bit word, with the lower 12 bits containing the
conversion result.
Table 15-2. Samples and FIFO Depth of Sequencers
Sequencer
SS3
SS2
SS1
SS0
Number of Samples
1
4
4
8
Depth of FIFO
1
4
4
8
For a given sample sequence, each sample is defined by bit fields in the ADC Sample Sequence
Input Multiplexer Select (ADCSSMUXn), ADC Sample Sequence Extended Input Multiplexer
Select (ADCSSEMUXn) and ADC Sample Sequence Control (ADCSSCTLn) registers, where
"n" corresponds to the sequence number. The ADCSSMUXn and ADCSSEMUXn fields select the
input pin, while the ADCSSCTLn fields contain the sample control bits corresponding to parameters
such as temperature sensor selection, interrupt enable, end of sequence, and differential input
mode. Sample sequencers are enabled by setting the respective ASENn bit in the ADC Active
Sample Sequencer (ADCACTSS) register and should be configured before being enabled. Sampling
is then initiated by setting the SSn bit in the ADC Processor Sample Sequence Initiate (ADCPSSI)
register. In addition, sample sequences may be initiated on multiple ADC modules simultaneously
using the GSYNC and SYNCWAIT bits in the ADCPSSI register during the configuration of each ADC
module. For more information on using these bits, refer to page 1112.
When configuring a sample sequence, multiple uses of the same input pin within the same sequence
are allowed. In the ADCSSCTLn register, the IEn bits can be set for any combination of samples,
allowing interrupts to be generated after every sample in the sequence if necessary. Also, the END
bit can be set at any point within a sample sequence. For example, if Sequencer 0 is used, the END
bit can be set in the nibble associated with the fifth sample, allowing Sequencer 0 to complete
execution of the sample sequence after the fifth sample.
After a sample sequence completes execution, the result data can be retrieved from the ADC
Sample Sequence Result FIFO (ADCSSFIFOn) registers. The FIFOs are simple circular buffers
that read a single address to "pop" result data. For software debug purposes, the positions of the
FIFO head and tail pointers are visible in the ADC Sample Sequence FIFO Status (ADCSSFSTATn)
registers along with FULL and EMPTY status flags. If a write is attempted when the FIFO is full, the
write does not occur and an overflow condition is indicated. Overflow and underflow conditions are
monitored using the ADCOSTAT and ADCUSTAT registers.
Module Control
Outside of the sample sequencers, the remainder of the control logic is responsible for tasks such
as:
■ Interrupt generation
■ DMA operation
June 18, 2014
Texas Instruments-Production Data
1065