A/D Conversion; Analog Input - Analog Devices adsp-2100 Manual

8 Analog Interface
Two ADSP-21msp58/59 interrupts are dedicated to the ADC and DAC
converters. One interrupt is used for the ADC and the other interrupt
is used for the DAC. Interrupts occur at the sample rate or when the
autobuffer transfer is complete.
A block diagram of the analog interface is shown in Figure 8.1, and pin
definitions are given in Table 8.1.
VIN
NORM
MUX
VIN
AUX
DECOUPLE
REF FILTER
V
BUF
REF
VOUT
P
VOUT
N
DIFFERENTIAL
OUTPUT AMP
Figure 8.1 Analog Interface Block Diagram (ADSP-21msp58/59)
8.2
The A/D conversion circuitry of the ADSP-21msp58/59's analog
interface consists of an input multiplexer, a programmable gain
amplifier (PGA), and a sigma-delta analog-to-digital converter (ADC).
8.2.1
The analog input is internally biased by an on-chip voltage reference to
allow operation of the ADSP-21msp58/59 with a single +5V power
supply. The analog inputs should be ac-coupled.
An analog multiplexer selects either the NORM or AUX input. The
input multiplexer is configured by bit 1 (IMS) of the
ADSP-21msp58/59's analog control register (which is memory-
mapped at address 0x3FEE in data memory). The multiplexer setting
should not be changed while an input signal is being processed.
8 – 2
ADC
PGA
VOLTAGE
REFERENCE
ANALOG
DAC
SMOOTHING
PGA
FILTER

A/D CONVERSION

Analog Input

16-BIT SIGMA-DELTA ADC
ANTI-ALIASING
ANALOG
1
SIGMA-DELTA DECIMATION
MODULATOR
FILTER
1.0
MHz
16-BIT SIGMA-DELTA DAC
1
DIGITAL 16
ANTI-IMAGING
SIGMA-DELTA
INTERPOLATION
MODULATOR
FILTER
1.0 1.0
MHz MHz
16 DIGITAL 16
HIGH-PASS
FILTER
8.0
8.0
kHz
kHz
16 16
DIGITAL
HIGH-PASS
8.0 FILTER 8.0
kHz kHz
16
PROCESSOR
INTERFACE