Freescale Semiconductor DSP56366 - Manual (Page 217)

DSP56366 24-Bit Digital Signal Processor User Manual, Rev. 4
Freescale Semiconductor 10-1
10 Digital Audio Transmitter
10.1 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 10-1 .
NOTE
The shaded registers in Figure 10-1 are directly accessible by DSP
instructions.