Intel PXA26X - Manual (Page 464)

13-2 Intel® PXA26x Processor Family Developer’s Manual
AC97 Controller Unit
13.3 Signal Description
The AC97 signals form the AC-link, which is a point-to-point synchronous serial interconnect that
supports full-duplex data transfers. All digital audio streams, modem line codec streams, and
command/status information are communicated over the AC-link. The AC-link uses general
purpose I/Os (GPIOs). Software must reconfigure the GPIOs to use them as the AC-link. The AC-
link pins are listed and described in
Table 13-1 .
13.3.1 Signal Configuration Steps
1. Configure SYNC and SDATA_OUT as outputs.
2. Configure BITCLK, SDATA_IN_0, and SDATA_IN_1 as inputs.
3. nACRESET is a GPIO that is out of reset a dedicated output. It remains asserted on power-up.
Complete these steps to de-assert nACRESET:
a. Configure the other AC97 signals as previously described.
b. In the Global Control Register (GCR), Set the GCR[COLD_RST] bit. Refer to
Table 13-8, “Global Control Register” on page 13-20 for more details.
Note: Refer to Section 4.1.3, “GPIO Register Definitions” on page 4-7 for details on programing the
GPDR and GAFR for use with the ACUNIT.
13.3.2 Example AC-link
Figure 13-1 shows an example interconnect for an AC-link. The ACUNIT supports one or two
codecs on the AC-link. SDATA_IN_1 is not needed if only a primary codec is connected.
Table 13-1. External Interface to Codecs
Name Direction Description summary
GP89/nACRESET O
Active-Low Codec Reset – The codec’s registers reset when nACRESET
is asserted.
GP28/BITCLK I 12.288-MHz-bit-rate clock.
GP31/SYNC O 48-KHz-frame indicator and synchronizer.
GP30/SDATA_OUT O Serial audio output data to codec for digital-to-analog conversion.
GP29/SDATA_IN_0 I Serial audio input data from primary codec.
GP32/SDATA_IN_1 I Serial audio input data from secondary codec.