SA9401 Ver la hoja de datos (PDF) - South African Micro Electronic Systems

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SA9401

UNIVERSAL PABX TONE GENERATOR

South African Micro Electronic Systems 

SA9401

EPROM Interface

The EPROM Interface controls all aspects of the transfer of program and tone data to

the SA9401. This module comprises seven distinct functions.

The Program Select Register reflects the settings on pins PS2 - PS0 which are latched

into the register at the start of every frame. The mapping of the pin settings to the

selected program is by a simple binary code (PS2 = msb).

The Cycle Register is loaded with a 9-bit value (CYCLE) indicating the number of

samples in a Tone Block (or basic waveform). It is assumed that all basic waveforms in

a single Tone Plan will have a common size.

Successive samples in a Tone Block are addressed by the 9-bit Sample Counter which

cycles through from zero to Cycle-1. The current value of this register and the contents

of the Cycle Register are fed to a Comparator which resets the counter after it reaches

the terminal value of Cycle-1.

The required Tone Block (or waveform) is addressed by the Tone Block Register. The

content of the register is a function of the Program Select and Cadence Controller.

As previously described, Tone Plans are defined in terms of a basic waveform (Tone

Block) and a Program of descriptive parameters which together are stored in an exter-

nal EPROM. Consequently a Data Fetch from the EPROM may retrieve either a Pro-

gram Instruction or a Tone Sample. In either case the Address Multiplexer constructs

the address according to the following table.

ADDRESS LINE

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

Program Instruction Fetch

1

0

0

0

PSEL2

PSEL1

PSEL0

PC6

PC5

PC4

PC3

PC2

PC1

PC0

Tone Sample Fetch

0

TONE_BLOCK.3

TONE_BLOCK.2

TONE_BLOCK.1

TONE_BLOCK.0

SAMPLE_COUNT.8

SAMPLE_COUNT.7

SAMPLE_COUNT.6

SAMPLE_COUNT.5

SAMPLE_COUNT.4

SAMPLE_COUNT.3

SAMPLE_COUNT.2

SAMPLE_COUNT.1

SAMPLE_COUNT.0

The details of the Address mapping will be described later in the External Data Stor-

age section

6

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