Functional Description

processor architecture that combines the signal processing

capabilities of a digital signal processor (DSP) with the

decision-making and data movement functionality of a

general-purpose 80C188 control microprocessor. This

dual-processor approach offloads many low-level decision-

making tasks from the host computer, enabling develop-

ment of more powerful applications.

This architecture

response time

incoming call

Each of four loop start telephone line interfaces on the

DIALOG/4 board receives analog voice and telephony

signaling information from the telephone network (see

block diagram). Each line interface uses reliable, solid-

state hook switches (no mechanical contacts) and FCC

part 68 class B ring detection circuitry. This FCC-

approved ring detector is less susceptible to spurious

rings created by random voltage fluctuations on the net-

work. Each interface incorporates circuitry that protects

against high-voltage spikes and adverse network condi-

tions, letting applications go off-hook any time during ring

cadence without damaging the board.

Inbound telephony signaling (ring and loop current detec-

tion) are conditioned by the line interface and routed via a

control bus to the control processor. The control proces-

sor responds to these signals, informs the application of

telephony signaling status, and instructs the line interface

to transmit outbound signaling (on-hook/off-hook) to the

telephone network.

The audio voice signal from the network is sent through a

bandpass filter, conditioned by the line interface, and then

applied to a COder/DECoder (CODEC) circuit. The

CODEC filters, samples, and digitizes the inbound analog

audio signal and passes the digitized signal to a

Motorola* DSP.

Based on Spring Ware firmware loaded in DSP RAM, the

DSP performs the following signal analysis and opera-

tions on this incoming data:

tions in the level of the incoming audio signal

(ADPCM) or Pulse Code Modulation (PCM) algorithm to

compress the digitized voice and save disk storage

space

application-defined single- or dual-frequency tone

and the caller is not responding

For outbound data, the DSP performs the following oper-

ations:

application or user request

defined general-purpose tone

3

Datasheet

Code/Data

DRAM

80C188

Control

Processor

Shared RAM

PC XT/AT BUS

DSP

CODEC

Line

Interface

To

Central

Office

or PBX

DSPRAM

IRQ

DATA

Control Bus

1 of 4 Shown