Texas Instruments Digital Signal Processor SM320F2812-HT User Manual
Page 58
Input Analog Voltage
ADCLO
4096
,
3
-
´
SGUS062B
–
JUNE 2009
–
REVISED JUNE 2011
4.3
Enhanced Analog-to-Digital Converter (ADC) Module
A simplified functional block diagram of the ADC module is shown in Figure 4-4. The ADC module
consists of a 12-bit ADC with a built-in sample-and-hold (S / H) circuit. Functions of the ADC module
include:
•
12-bit ADC core with built-in S/H
•
Analog input: 0.0 V to 3.0 V (Voltages above 3.0 V produce full-scale conversion results.)
•
Fast conversion rate: 80 ns at 25-MHz ADC clock, 12.5 MSPS
•
16-channel, MUXed inputs
•
Autosequencing capability provides up to 16 autoconversions in a single session. Each conversion can
be programmed to select any 1 of 16 input channels
•
Sequencer can be operated as two independent 8-state sequencers or as one large 16-state
sequencer (i.e., two cascaded 8-state sequencers)
•
Sixteen result registers (individually addressable) to store conversion values
–
The digital value of the input analog voltage is derived by:
Digital Value = 0,
when input
≤
0 V
Digital Value =
when 0 v
<
input
<
3 V
Digital Value = 4095,
when input
≥
3 V
•
Multiple triggers as sources for the start-of-conversion (SOC) sequence
–
S/W - software immediate start
–
EVA - Event manager A (multiple event sources within EVA)
–
EVB - Event manager B (multiple event sources within EVB)
•
Flexible interrupt control allows interrupt request on every end-of-sequence (EOS) or every other EOS
•
Sequencer can operate in start/stop mode, allowing multiple time-sequenced triggers to synchronize
conversions
•
EVA and EVB triggers can operate independently in dual-sequencer mode
•
Sample-and-hold (S/H) acquisition time window has separate prescale control
The ADC module in the F2812 has been enhanced to provide flexible interface to event managers A and
B. The ADC interface is built around a fast, 12-bit ADC module with a fast conversion rate of 80 ns at
25-MHz ADC clock. The ADC module has 16 channels, configurable as two independent 8-channel
modules to service event managers A and B. The two independent 8-channel modules can be cascaded
to form a 16-channel module. Although there are multiple input channels and two sequencers, there is
only one converter in the ADC module.
shows the block diagram of the F2812 ADC module.
The two 8-channel modules have the capability to autosequence a series of conversions, each module
has the choice of selecting any one of the respective eight channels available through an analog MUX. In
the cascaded mode, the autosequencer functions as a single 16-channel sequencer. On each sequencer,
once the conversion is complete, the selected channel value is stored in its respective RESULT register.
Autosequencing allows the system to convert the same channel multiple times, allowing the user to
perform oversampling algorithms. This gives increased resolution over traditional single-sampled
conversion results.
58
Peripherals
Copyright
©
2009
–
2011, Texas Instruments Incorporated
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