Motorola DSP56012 6.1 INTRODUCTION

Serial Audio Interface
Introduction
MOTOROLA DSP56012 User’s Manual 6-3
6.1 INTRODUCTION
The DSP communicates with data sources and sinks through its Serial Audio
Interface (SAI). The SAI is a synchronous serial interface dedicated for audio data
transfers. It provides a full duplex serial port for serial connection with a variety of
audio devices, such as Analog-to-Digital (A/D) converters, Digital-to-Analog (D/A)
converters, CD devices, etc. The SAI implements a wide range of serial data formats
currently in use by audio manufacturers. Examples are:
•I
2S (Inter Integrated-circuit Sound) format (Philips)
• CDP format (Sony)
• MEC format (Matsushita)
• Most Industry-Standard A/D and D/A
The SAI consists of independent transmit and receive sections and a shared
baud-rate generator. The transmitter and receiver sections may each operate in either
the Master or Slave mode. In the Master mode the serial clock and the word select
lines are driven internally according to the baud-rate generator programming. In the
Slave mode these signals are supplied from an external source. The transmitter
consists of three transmit-data registers, three fully synchronized output-shift
registers, and three serial-data output lines controlled by one transmitter controller.
This permits data transmission to one, two, or three stereo audio devices
simultaneously. The receiver consists of two receive-data registers, two fully
synchronized input-shift registers, and two serial data input lines controlled by one
receiver controller. This permits data reception from one or two stereo audio devices
simultaneously.
The following is a short list of the SAI features:
• Programmable serial clock generator with high resolution:
fsck = fosc/2i (for i > 1)
• Maximum external serial clock rate equal to one third of the DSP core clock
• Separate transmit and receive sections
• Master or Slave operating modes
• Three synchronized data transmission lines
• Two synchronized data reception lines
• Double-buffered