Stereo System User Manual

Digital Audio Transmitter
Overview
MOTOROLA DSP56012 User’s Manual 8-3
8.1 OVERVIEW
The Digital Audio Transmitter (DAX) is a serial audio interface module that outputs
digital audio data in the AES/EBU, CP-340 and IEC958 formats. Some of the key
features of the DAX are listed below.
• Operates on a frame basis—The DAX can handle one frame (consisting of
two sub-frames) of audio and non-audio data at a time.
• Double-buffered audio and non-audio data—The DAX data path is
double-buffered so the next frame data can be stored in the DAX without
affecting the frame currently being transmitted.
• Programmable clock source—Users can select the DAX clock source, and this
selection configures the DAX to operate in Slave or Master mode.
• Supports both Master mode and Slave mode in a digital audio network—If
the user selects a divided DSP core clock, the DAX will operate in the Master
mode. If the user selects an external clock source, the DAX will operate in the
Slave mode.
The accessible DAX registers are all mapped in the X I/O memory space. This allows
programmers to access the DAX using standard instructions and addressing modes.
Interrupts generated by the DAX can be handled with a fast interrupt for cases in
which the non-audio data does not change from frame to frame. When the DAX
interrupt is disabled, it can still be served by a “polling” technique. A block diagram
of the DAX is shown in Figure 8-1.
Note: The shaded registers in Figure 8-1 are directly accessible by DSP instructions.