Stereo System User Manual

Serial Audio Interface
Serial Audio Interface Programming Model
MOTOROLA DSP56012 User’s Manual 6-9
6.3.1 Baud Rate Control Register (BRC)
The serial clock frequency is determined by the control bits in the Baud Rate Control
register (BRC) as described in the following paragraphs. The BRC is illustrated in
Figure 6-4 on page 6-8. The maximum allowed internally generated bit clock
frequency is f
osc
/4 and the maximum allowed external bit clock frequency is f
osc
/3.
BRC bits should be modified only when the baud-rate generator is disabled (i.e.,
when both receiver and transmitter sections are defined as slaves or when both are in
the individual reset state); otherwise improper operation may result. When read by
the DSP, the BRC appears on the two low-order bytes of the 24-bit word, and the
high-order byte is read as 0s. The BRC is cleared during hardware reset and software
reset.
Table 6-1 SAI Interrupt Vector Locations
Interrupt TXIL = 0 TXIL = 1 RXIL = 0 RXIL = 1
Left Channel Transmit P: $0010 P: $0040 — —
Right Channel Transmit P: $0012 P: $0042 — —
Transmit Exception P: $0014 P: $0044 — —
Left Channel Receive — — P: $0016 P: $0046
Right Channel Receive — — P: $0018 P: $0048
Receive Exception — — P: $001A P: $004A
Table 6-2 SAI Internal Interrupt Priorities
Priority Interrupt
Highest SAI Receive
SAI Transmit
SAI Left Channel Receive
SAI Left Channel Transmit
SAI Right Channel Receive
Lowest SAI Right Channel Transmit