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by AN1241/D

AN1241

©MOTOROLA, INC., 1995

AN1241/D

Interfacing the MC68HC705J1A to

9356/9366 EEPROMs

By Mark Glenewinkel

CSIC Applications

INTRODUCTION

This application note describes the hardware and software interface used to communicate between the

Freescale MC68HC705J1A MCU and 9356/9366 EEPROM chips. The 93XX series of EEPROMs are an

industry standard used widely to store nonvolatile bits of information. The software listing in this application

note will work with 9356 and 9366 EEPROMs. The EEPROM bits are arranged in 128 or 256 16-bit

registers, respectively. With some modification, the software will work with other 93XX series EEPROMs.

Some of the applications in which EEPROMs can be utilized are listed below.

•

ID number for remote addressing or security

•

Storage of telecommunication information like phone number recall and speed dialing

•

Power down information storage for consumer electronics like TVs and VCRs

•

Reprogrammable calibration data for test/measurement equipment

The 93XX EEPROMs communicate with the outside world using a serial link. Since the MC68HC705J1A

does not have the hardware on chip to communicate to the EEPROM, a software driver is used. This

method bit programs an I/O port to properly transfer data to and from the EEPROM. A National

NM93C56N was used for testing the software routines in this application note.

HARDWARE INTERFACE

The 9356 is a very simple 8-pin device. Appendix A shows a typical connection between the

MC68HC705J1A and the 9356. The serial interface connection uses only four pins of the 9356. They are

as follows:

•

CS — Chip Select

•

SK — Serial Clock

•

DO — Serial Data Output

•

DI

— Serial Data Input

These signals must be clocked in a certain way in order to transfer the correct serial data to and from the

MC68HC705J1A.

For More Information On This Product,

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Freescale Semiconductor