ST18-AU1 データシートの表示（PDF） - STMicroelectronics

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ST18-AU1

SIX-CHANNEL DOLBY AC3/MPEG2 AUDIO DECODER

STMicroelectronics 

ST18-AU1

Table 2.2 Direct X bus extension / Bus extension through bus switch unit (39 pins)

Pin name

ED0-15

EA0-15

EIRD

EIWR

XBSE

EYRD

EYWR

XRDE_EXRD

XWRE_EXWR

Type

I/O

O

O

O

O

O

O

O

O

Description

Bus switch unit (BSU) X/Y/I data extension bus.

BSU X/Y/I address extension bus.

BSU I-extension bus read strobe EIRD output.

BSU I-extension bus write strobe EIWR output.

X_extension bus data strobe (BSU not used).

BSU Y-extension bus read strobe EYRD output.

BSU Y-extension bus write strobe EYWR output.

Multiplexed output.

In direct X-bus extension mode (BSU not used):

X-extension bus read strobe (XRDE). Active low when reading from exter-

nal X-memory.

In X extension through BSU mode:

BSU X-extension bus read strobe (EXRD). Active low when reading from

external memory (when bit I/M of XER register is ‘1’: Intel mode).

BSU extension bus data strobe (EDS). Active low when reading from or writ-

ing to external memory (when bit I/M of XER register is ‘0’ Motorola mode).

Multiplexed output.

In direct X-bus extension mode (BSU not used):

X-extension bus write strobe (XWRE). Active low when writing to external

X-memory.

In X extension through BSU mode:

BSU X-extension bus write strobe (EXWR). Active low when writing to ex-

ternal memory (when bit I/M of XER register is ‘1’: Intel mode).

Extension bus read /write signal (ERD_WR). Low during write cycle, other-

wise high (when bit I/M of XER register is ‘0’: Motorola mode).

Table 2.3 General purpose parallel port (8 pins)

Pin name

P0-7

Type

I/O

Description

Parallel port I/O. Each pin can be programmed as input or output.

On reset, all pins are inputs.

8/87

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