Motorola DSP56012 - Manual (Page 191)

Serial Audio Interface
Serial Audio Interface Programming Model
MOTOROLA DSP56012 User’s Manual 6-13
6.3.2.8 RCS Receiver Clock Polarity (RCKP)—Bit 8
The read/write Receiver Clock Polarity (RCKP) control bit selects the polarity of the
receiver serial clock. When RCKP is cleared, the receiver clock polarity is negative.
When RCKP is set, the receiver clock polarity is positive. Negative polarity means
that the Word Select Receive (WSR) and Serial Data In (SDIx) lines change
synchronously with the negative edge of the clock, and are considered valid during
positive transitions of the clock. Positive polarity means that the WSR and SDIx lines
change synchronously with the positive edge of the clock, and are considered valid
during negative transitions of the clock (see Figure 6-7). The RCKP bit is cleared
during hardware reset and software reset.
6.3.2.9 RCS Receiver Relative Timing (RREL)—Bit 9
The read/write Receiver Relative timing (RREL) control bit selects the relative timing
of the Word Select Receive (WSR) signal as referred to the serial data input lines
(SDIx). When RREL is cleared, the transition of WSR, indicating start of a data word,
occurs together with the first bit of that data word. When RREL is set, the transition
of WSR occurs one serial clock cycle earlier (together with the last bit of the previous
data word), as required by the I
2
S format (see Figure 6-8). The RREL bit is cleared
during hardware reset and software reset.
Figure 6-7 Receiver Clock Polarity (RCKP) Programming
SDI
SCKR
RCKP = 0
SDI
SCKR
RCKP = 1
WSR WSR
AA0433