AD1845 Analog Devices, AD1845 Datasheet - Page 9

• Manufacturer Part Number: AD1845
• Description: Parallel-port 16-Bit Soundport Stereo Codec
• Manufacturer: Analog Devices

The AD1845 has built-in 8/16 mA (user selectable) bus drivers.
If 24 mA drive capability is required, the AD1845 generates
enable and direction controls for IC bus buffers such as the
74 245.
The codec includes a stereo pair of
verters and a stereo pair of
AD1845 mixer surpasses MPC Level-2 recommendations. In-
puts to the ADC can be selected from four stereo pairs of analog
signals: line (LINE), microphone (MIC), auxiliary line #1
(AUX1), and post-mixed DAC output. A software-controlled
programmable gain stage allows independent gain for each
channel going into the ADC. In addition, the analog mixer al-
lows the mono input (M_IN), MIC, AUX1, LINE and auxiliary
line #2 (AUX2) signals to be mixed with the DACs’ output.
The ADCs’ output can be digitally mixed with the DACs’ input.
The pair of 16-bit outputs from the ADCs is available over a
byte-wide bidirectional interface that also supports 16-bit digital
input to the DACs and control information. The AD1845 can
accept and generate 16-bit twos complement PCM linear digital
data, 8-bit unsigned magnitude PCM linear data, and 8-bit
REV. B
Power Supplies
Pin Name
V
GNDA
V
GNDD
(Continued from page 1)
-law or A-law companded digital data.
CC
DD
AD1845
DATA7:0
DBDIR
PDRQ
CDRQ
CDAK
DBEN
PDAK
WR
INT
CS
RD
A1
A0
Figure 1. Interface to ISA Bus
PLCC
35 & 36
34 & 37
1, 7, 15,
19, 45,
54
2, 8, 16,
20, 25,
44, 53,
64
8
B
DIR
G
ADDRESS
DECODE
74_245
digital-to-analog converters. The
A
analog-to-digital con-
TQFP
41 & 42
40 & 43
10, 14,
55, 68,
88, 98
11, 15, 20,
54, 67,
79, 89,
99
8
18
AEN
SA19:2
SA1
SA0
IOWC
IORC
DATA7:0
DRQ <X>
DRQ <Y>
DAK <X>
DAK <Y>
IRQ <Z>
S
A
B
U
S
I
I/O
I
I
I
I
–9–
The
attenuator provides independent user volume control over each
DAC channel. Nyquist images and shaped quantized noise are
removed from the DACs’ analog stereo output by on-chip
switched-capacitor and continuous-time filters.
The AD1845 supports multiple low power and power-down
modes to support notebook and portable computing multimedia
applications. The ADC, DAC, and mixer paths can be sus-
pended independently allowing the AD1845 to be used for
capture-only or playback-only, lessening power consumption
and extending battery life.
The AD1845 includes a variable sample frequency generator,
that allows the codec to instantaneously change sample rates
with a resolution of 1 Hz without “clicks” and “pops”. Addi-
tionally,
band regardless of the chosen sample rate. The codec uses the
variable sample frequency generator to derive all internal clocks
from a single external crystal or clock source.
Expanded Mode (MODE2)
MODE1 is the initial state of the AD1845. In this state the
AD1845 appears as an AD1848 compatible device. To access
the expanded modes of operation on the AD1845, the MODE2
bit should be set in the Miscellaneous Information Control
Register. When this bit is set to one, 16 additional indirect reg-
isters can be addressed allowing the user to access the AD1845’s
expanded features. The AD1845 can return to MODE1 opera-
tion by clearing the MODE2 bit.
The additional MODE2 functions are:
1. Full-Duplex DMA support.
2. MIC input mixer, mute and volume control.
3. Mono output with mute control.
4. Mono input with mixer volume control.
5. Software controlled advanced power-down modes.
6. Programmable sample rates from 4 kHz to 50 kHz in 1 Hz
7. Capture/Playback FIFO enable/disable.
increments.
DACs are preceded by a digital interpolation filter. An
quantization noise is kept out of the 20 kHz audio
Description
Analog Supply Voltage (+5 V).
Analog Ground.
Digital Supply Voltage (+5 V).
Digital Ground.
AD1845