AM79C30A datasheet(13/101 Pages) AMD

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Am79C30A/32A Data Sheet

FUNCTIONAL DESCRIPTION

Microprocessor Interface (MPI)

The Am79C30A/32A can be connected to any general

purpose 8-bit microprocessor via the MPI. The MCLK

from the Am79C30A/32A can be used as the clock for

the microprocessor. The MPI is an interrupt-driven in-

terface containing all the circuitry necessary for access

to the internal programmable registers, status regis-

ters, coefficient RAM, and transmit/receive buffers.

MPI External Interface

External connections to the MPI are shown in Table 5.

Direct Registers

Access to the Direct Registers of the Am79C30A/32A

is controlled by the state of the CS, RD, WR, A2, A1,

and A0 input pins, as defined below by Table 6.

Indirect Registers

To read from or write to any of the Indirect Registers, an

indirect address command is first written to the Com-

mand Register (CR). One or more data bytes may then

be transferred to or from the selected register through

the Data Register (DR).

Registers within certain groups can be accessed

quickly by using internal circuitry which automatically

increments the indirect value. In Table 7, the bytes

transferred numbers are the number of bytes which are

read or written to the DR after the CR has been loaded.

Whenever the CR is loaded, any previous commands

are automatically terminated.

Note:

The RD and WR signals must never both be Low under normal operating conditions.

Table 5.

MPI External Interface

Name

Direction

Function

D7–D0

Bidirectional

Data Bus

A2–A0

Inputs

Address Line

Input

Read Enable

Input

Write Enable

Input

Chip Select

RESET

Input

Initialization

INT

Output

Interrupt

Table 6.

Direct Register Access Guide

Mode

0100

Command Register (CR)

0010

Interrupt Register (IR)

0100

Data Register (DR)

0010

Data Register (DR)

0010

D-channel Status Register 1 (DSR1)

0010

D-channel Error Register (DER) (2-byte FIFO)

0101

D-channel Transmit buffer (DCTB) (8- or 16-byte FIFO)

0011

D-channel Receive buffer (DCRB) (8- or 32-byte FIFO)

0101

Bb-channel Transmit buffer (BBTB)

0011

Bb-channel Receive buffer (BBRB)

0101

Bc-channel Transmit buffer (BCTB)

0011

Bc-channel Receive buffer (BCRB)

0011

D-channel Status Register 2 (DSR2)

No access (X = logical 0 or 1)

—

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