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SECTION
DIGITAL AUDIO TRANSMITTER
12.1
INTRODUCTION
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
subframes) 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.
•
Direct Memory Access—Audio data and non-audio data can be written to the DAX
using DMA.
•
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.
•
GPIO—Each of the two DAX pins can be configured as either GPIO or as specific
DAX pin. Each pin is independent of the other. However, at least one of the two pins
must be selected as a DAX pin to release the DAX from reset.
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 interrupts are disabled, they can
still be served by DMA or by a "polling" technique. A block diagram of the DAX is shown in
Figure 12-1.
MOTOROLA
12
DSP56367
12-1
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