Cirrus Logic CS8420 - Manual (Page 13)

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CS8420
3. GENERAL DESCRIPTION
The CS8420 is a fully asynchronous sample rate converter plus AES3 transceiver intended to be used in digital au-
dio systems. Such systems include digital mixing consoles, effects processors, tape recorders, and computer mul-
timedia systems. The CS8420 is intended for 16-, 20-, and 24-bit applications where the input sample rate is
unknown, or is known to be asynchronous to the system sample rate.
On the input side of the CS8420, AES3 or 3-wire serial format can be chosen. The output side produces both AES3
and 3-wire serial format. An I²C/SPI-compatible microcontroller interface allows full block processing of channel sta-
tus and user data via block reads from the incoming AES3 data stream and block writes to the outgoing AES3 data
stream. The user can also access information decoded from the input AES3 data stream, such as the presence of
non-audio data and pre-emphasis, as well as control the various modes of the device. For users who prefer not to
use a micro-controller, six hardware modes have been provided and documented towards the end of this data sheet.
In these modes, flexibility is limited, with pins providing some programmability.
When used for AES3-input/AES3-output applications, the CS8420 can automatically transceive user data that con-
forms to the IEC60958-recommended format. The CS8420 also allows access to the relevant bits in the AES3 data
stream to comply with the serial copy management system (SCMS).
The diagram on the cover of this data sheet shows the main functional blocks of the CS8420. Figure 5 shows the
supply and external connections to the device.
Familiarity with the AES3 and IEC60958 specifications are assumed throughout this document. Application Note 22:
Overview of Digital Audio Interface Data Structures, contains a tutorial on digital audio specifications. The paper An
Understanding and Implementation of the SCMS Serial Copy Management System for Digital Audio Transmission,
by Clif Sanchez, is an excellent tutorial on SCMS. It may be obtained from Cirrus Logic, Inc., or from the AES.
To guarantee system compliance, the proper standards documents should be obtained. The latest AES3 standard
should be obtained from the Audio Engineering Society (ANSI), the latest IEC60958 standard from the International
Electrotechnical Commission and the latest EIAJ CP-1201 standard from the Japanese Electronics Bureau.