User manual

9.2 ADSP-2181 DSP
The ADSP-2181 is a 24-bit instruction, 16-bit data, 33 million instruc-
tions per second (MIPS) DSP. The DSP is described in “Analog
Devices ADSP-2181 DSP Microcomputer data sheet, Rev. A.”
Additional information is provided in the ADSP-2100 Family User’s
Manual. 1993. Analog Devices, (Prentice-Hall, ISBN 0-13-006958-2.)
The DSP is the heart of the real time signal processing engine - it works
in conjunction with an AD1847 16-bit stereo CODEC that forms the
interface to the analog world. The AD1847 is described in the “Analog
Devices AD1847 Serial Port 16-bit SoundPort Stereo Codec. Data sheet
Rev. 0.”
The CODEC contains two separate 16-bit A/D-D/A channels, each with
their respective analog signal conditioning hardware. This allows two
independent analog I/O signals to be processed simultaneously, for
instance when serving a cross-band digital communications application.
The CODEC hardware, however, requires that the operating modes of
the channels are initialized to work identically.
9.3 Zilog 85C30 SCC
Although the DSP is capable of handling relatively high rate HDLC data
streams in firmware, it is evident that the processing load associated
with implementing two parallel DSP modems in addition to clock
extraction, HDLC framing and inter-processor communications, this
task best be taken care of by dedicated hardware specially designed for
this task. The Zilog SCC is a suitable device that meets this description.
The SCC can be programmed to be used for either asynchronous data
communications processing for Baudot or ASCII modes at various bit
rates, or for decoding HDLC streams at various bit rates. On-board
hardware is provided to allow the SCC to use its internal DPLL to per-
form clock extraction.
Interfacing the SCC with the DSP is via four programmable flag (PF)
pins. Two flags serve for input to the DSP that is utilized for output tone
synthesis - the other two flags serve as serial data drivers that supply
data to the SCC.
High speed HDLC data I/O between the SCC and the 386EX may be
handled under interrupt control. The necessary drivers need to be
installed and armed at the 386 side.
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