Innes Corporation Pty Ltd
3/38 Leighton Pl
Hornsby, NSW 2077, Australia
Phone: +61 2 9987 0499
Fax: +61 2 9987 0599
E-mail:
sales@innescorp.com.au
Website: http://www.innescorp.com.au
16
Auricon 2.2 & 4.1 Manual
Functional Description
The balanced audio inputs are buffered, attenuated and filtered prior to being coupled into the
A/D converters. From the D/A converters, differential line driver amplifiers provide a maximum
output level of +24dBm and also incorporate low pass filtering to attenuate the out-of-band
noise produced by the converters.
Digitized audio is passed in serial form between the converters and the Analog Devices
ADSP21065L digital signal processor. The DSP provides a circular buffer as short term FIFO
storage to cover latency times between PCI transfers, and also performs the sampling rate
conversion, level adjustment and mixing functions. Host-initiated bus mastering is used for
audio data transfer through the PLX PCI9054 PCI interface.
The converters operate at a sampling rate of 49kHz (this frequency allows efficient sampling
rate conversion to all the standard rates). Clocking for the converters, serial data transfer and
DSP is provided from a 25.088MHz precision crystal oscillator.
Configuration data for the PCI interface is stored in a serial EEPROM which is programmed in
the factory during initial setup of the board.
The DSP software is uploaded from the PC whenever the Auricon device driver is started. The
Auricon supports standby and hibernation power management modes.
A filtered analogue 5V plane is used in order to minimise any digital noise on the analogue
inputs and outputs. The analogue ground is also fenced off from the digital ground, and clock
and serial data signals crossing the ground plane division are filtered.
