
PSB 7280
Semiconductor Group
22
Data Sheet 1998-07-01
Two receive and two transmit audio channels are provided. They are input/output on the
ISDN Oriented Modular
(IOM-2) or the
Serial Audio Interface
(SAI)
interfaces in
individually programmable time-slots. These channels are accessed from the DSP
and/or the parallel host interface.
The two
HDLC Controller
channels can be serviced by the DSP or the parallel host
interface. The serial data for the HDLC controllers are located in programmable
time-slots on IOM-2 and/or SAI.
For development purposes, the
External Memory Interface
allows programs to be
executed from an external memory and external data memory to be used.
2.2
Functions
2.2.1
The main functions implemented by the PSB 7238 are:
– G.728 compression/decompression (16 kbit/s)
– G.722 compression/decompression for 7-kHz audio (64, 56, 48 kbit/s)
– G.711 compression/decompression (64 kbit/s)
– Digital sampling rate conversion (16 kHz - 8 Hz) for G.722 audio with 8-kHz codec
(bandwidth reduced to 3.4 kHz)
– Accepts/outputs uncompressed audio 8-bit PCM A/
μ
law or 16-bit linear format
– Uncompressed/compressed
audio
switchable
combinations (IOM/Serial Audio Interface, IOM/Host, Host/Host)
– Inband controlled H.221/H.223 oriented audio protocol, e.g. for direct serial
connection to videocodec (VCP of 8
×
8 Inc., formerly IIT Inc.)
– Outband controlled audio protocol with optimized data rate
– Stable reaction on interrupt handshake timing violations of e.g. a slow host
(Windows
PC)
For more details on the hardware (necessary for a better understanding of some of the
topics described in the present chapter), please refer to the other chapters of this data
sheet.
Summary of the Functions
between
different
interface