Stereo System User Manual

2-18 DSP56012 User’s Manual MOTOROLA
Signal Descriptions
General Purpose Input/Output (GPIO)
2.9 GENERAL PURPOSE INPUT/OUTPUT (GPIO)
2.10 DIGITAL AUDIO INTERFACE (DAX)
Table 2-10 General Purpose I/O (GPIO) Signals
Signal
Name
Signal Type
State during
Reset
Signal Description
GPIO0–
GPIO7
Input or
Output
(standard or
open-drain)
Disconnected
internally
General Purpose Input/Output—These signals
are used for control and handshake functions
between the DSP and external circuitry. Each
GPIO signal may be individually programmed to
be one of four states:
• Not connected
• Input
• Standard output
• Open-drain output
Table 2-11 Digital Audio Interface (DAX) Signals
Signal Name Type
State During
Reset
Signal Description
ADO Output Output, driven
high
Digital Audio Data Output—This signal is an
audio and non-audio output in the form of
AES/EBU, CP340 and IEC958 data in a biphase
mark format. The signal is driven high when the
DAX is disabled, and during hardware or software
reset.
ACI Input Tri-stated Audio Clock Input—This is the DAX clock input.
When programmed to use an external clock, this
input supplies the DAX clock. The external clock
frequency must 256, 384, or 512 times the audio
sampling frequency (256 x Fs, 384 x Fs or 512 x Fs,
respectively). The ACI signal is high impedance
(tri-stated) only during hardware or software reset.
If the DAX is not used, connect the ACI signal to
ground through an external pull-down resistor to
ensure a stable logic level at the input.