PSD833F2 datasheet(60/128 Pages) STMICROELECTRONICS

60 / 128 page

MCU bus interface

PSD8XXFX

60/128

Doc ID 7833 Rev 7

15.1

PSD interface to a multiplexed 8-bit bus

Figure 18 shows an example of a system using a MCU with an 8-bit multiplexed bus and a

PSD. The ADIO port on the PSD is connected directly to the MCU address/data bus.

Address Strobe (ALE/AS, PD0) latches the address signals internally. Latched addresses

can be brought out to port A or B. The PSD drives the ADIO data bus only when one of its

internal resources is accessed and Read Strobe (RD, CNTL1) is active. Should the system

address bus exceed sixteen bits, ports A, B, C, or D may be used as additional address

inputs.

Figure 18.

An example of a typical 8-bit multiplexed bus interface

15.2

PSD interface to a non-multiplexed 8-bit bus

Figure 19 shows an example of a system using a MCU with an 8-bit non-multiplexed bus

and a PSD. The address bus is connected to the ADIO port, and the data bus is connected

to port A. port A is in tri-state mode when the PSD is not accessed by the MCU. Should the

system address bus exceed sixteen bits, ports B, C, or D may be used for additional address

inputs.

15.3

Data Byte Enable reference

MCUs have different data byte orientations. Table 18 shows how the PSD interprets

byte/word operations in different bus WRITE configurations. Even-byte refers to locations

with address A0 equal to '0' and odd byte as locations with A0 equal to ’1.’

MCU

BHE

ALE

RESET

AD [ 7:0]

A[ 15:8]

A[ 15: 8]

A[ 7: 0]

ADIO

PORT

WR (CNTRL0)

RD (CNTRL1)

BHE (CNTRL2)

RST

ALE (PD0)

PORT D

(OPTIONAL)

PSD

AI02878C

Obsolete

Product(s)

- Obsolete

Product(s)

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