Motorola DSP56012 - Manual (Page 216)

8-6 DSP56012 User’s Manual MOTOROLA
Digital Audio Transmitter
DAX Programming Model
The second sub-frame transmission (Channel B) starts with the preamble generator
generating the Channel B preamble (Y-preamble). At the same time, Channel B audio
and non-audio data is transferred to the XADSR shift-register from the XADBUF and
XNADBUF registers. The generated Y-preamble is output immediately after the
Channel A parity and is followed by the audio and non-audio data in the XADSR,
which is in turn followed by the calculated parity for Channel B. This completes a
frame transmission. When the Channel B parity is sent, the audio data for the next
frame, stored in the XADRA/XADRB and the non-audio data bits from the XCTR,
are uploaded.
8.4 DAX PROGRAMMING MODEL
The programmer-accessible DAX registers are shown in Figure 8-2 on page 8-7. The
registers are described in the following subsections. The Interrupt Vector table for the
DAX is shown in
Table 8-1 . The internal interrupt priority is shown in Table 8-2 .
8.5 DAX INTERNAL ARCHITECTURE
Hardware components shown in Figure 8-1 on page 8-4 are described in the
following sub-sections. The DAX programming model is illustrated in Figure 8-2 .
Table 8-1 DAX Interrupt Vectors
Condition Address Description
XADE & XAUR P:$0050 DAX Transmit Underrun Error
XADE & XBLK P:$0052 DAX Block Transferred
XADE P:$0056 DAX Transmit Register Empty
Table 8-2 DAX Interrupt Priority
Priority Interrupt
highest DAX Transmit Underrun Error
DAX Block Transferred
lowest DAX Transmit Register Empty