AD1812

REV. 0

–17–

SYSTEM TIMING AND CONTROL

If the AD1812 is not connected directly to the OSC clock on the

ISA bus, a single fundamental-mode and parallel-tuned

14.31818 MHz crystal oscillator can be substituted to derive all

timing parameters. Future feature enhanced, pin-compatible

versions of the SoundPort Controller will require a 33 MHz

clock or crystal input. Analog Devices suggests developing board

layouts that can be easily modified to supply the new clock.

DATA AND CONTROL TRANSFERS

The embedded SoundPort Stereo Codec supports a DMA

request/grant architecture for transferring data with the host

computer bus. One or two 8-bit or 16-bit DMA channels can

be supported. Programmed I/O (PIO) mode is also supported

for control register accesses and for applications lacking DMA

control. PIO transfers can be made on one channel while the

other is performing DMA. Transfers to and from the AD1812

are asynchronous relative to the internal data conversion clock.

Transfers are buffered by FIFOs located in the capture and

playback paths.

REFERENCE DESIGNS AND DEVICE DRIVERS

Reference designs and device drivers using the AD1812 are

available via Bulletin Board Service. The Computer Products

Division runs a BBS that can be reached at speeds up to 14,400

baud, no parity, 8 bits data, 1 stop bit, by dialing (617) 461-

4258. The BBS supports: V.32bis, error correction (V.42 and

MNP classes 2, 3, and 4), and data compression (V.42bis and

MNP class 5). Reference designs can also be found in the

AD1812 SoundPort Controller Technical Reference which can

be obtained by contacting your local Analog Devices sales repre-

sentative or authorized distributor. You can also find us on the

World Wide Web at http://www.analog.com.

FREQUENCY RESPONSE PLOTS

10

–90

–120

0

1.0

0.1

0.2

0.4

0.5

0.6

0.7

0.8

0.9

0

–80

–100

–110

–50

–70

–40

–60

–20

–10

–30

0.3

(Full-Scale Line-Level Inputs, –1 dB Gain)

10

–90

–120

0.40

0.44

0.48

0.56

0.60

0.64

0.68 0.70

0

–80

–100

–110

–50

–70

–40

–60

–20

–10

–30

0.52

Figure 9. Analog-to-Digital Frequency Response —

Transition Band (Full-Scale Line-Level Inputs,

–1 dB Gain)

10

–90

–120

0

1.0

0.1

0.2

0.4

0.5

0.6

0.7

0.8

0.9

0

–80

–100

–110

–50

–70

–40

–60

–20

–10

–30

0.3

(Full-Scale Inputs, 0 dB Attenuation)

10

–90

–120

0.40

0.44

0.48

0.56

0.60

0.64

0.68 0.70

0

–80

–100

–110

–50

–70

–40

–60

–20

–10

–30

0.52

Figure 11. Digital-to-Analog Frequency Response —

Transition Band (Full-Scale Inputs, 0 dB Attenuation)