XM28C040 datasheet(15/17 Pages) XICOR

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XM28C040

MultiPlane Architecture

The design of the XM28C040 has implemented a mul-

tiplane architecture. That is, there are four independent

128K x 8 memory spaces or planes, each selected by its

own chip enable input via the on-board decoder chip.

This architecture can be utilized in a number of ways.

Separate Data and Program Memory Spaces

The multiplane concept allows the system to write to one

plane of the module and still be able to read (continue

executing code) from the module, utilizing any plane not

performing a write operation.

This concept of separate data and program spaces can

be expanded by providing a simple off-module circuit

that will disable writes to predetermined portions of

memory. A very basic version is shown in the Functional

Diagram. Whenever A18 is HIGH, the WE input is forced

HIGH, write protecting one half the module. This half

would be reserved for read only program store while the

other half would be available for read and write data

store.

Expanded Sequential Page Lengths

A standard system implementation would be decoding

externally the module's chip enable and then wiring

each address of the module to its corresponding ad-

dress line in the system. This would effectively provide

the system a memory organized as four separate memory

planes with a sequential page address space of 256

bytes.

In an application such as data logging, the most efficient

method of logging the data is in a sequential manner. If

the data come in bursts that exceed 256 bytes in length

a longer page might be desirable. By swapping address

lines externally the effective page length can be ex-

panded to 1024 bytes. Refer to the table below for a

matrix illustrating the various page length options.

TABLE 1.

ADDRESS TRANSLATION MATRIX

Effective

A0-A7

A8-A16

A17

A18

Page Size

No. of

Planes

A0-A7

A8-A16

A17

A18

256

A0-A7

A9-A17

A18

512

A0-A7

A10-A18

1024

3873 PGM T09

System

Address

Lines

Module Address Inputs

Note:

The user should be aware the overall ICC of the module will increase as more individual components on the module are activated.

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