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PDF AN1241 Data sheet ( Hoja de datos )
| Número de pieza | AN1241 | |
| Descripción | Interfacing the MC68HC705J1A to 9356/9366 EEPROMs | |
| Fabricantes | Freescale Semiconductor | |
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AN1241
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.
©MOTOROLA, INC., 1995
For More Information On This Product,
Go to: www.freescale.com
AN1241/D
1 page  
Freescale Semiconductor, Inc.
AN1241/D
For More Information On This Product,
Go to: www.freescale.com
5
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Freescale Semiconductor, Inc.
*****************************************************************************
*
**
* Equates and RAM Storage
*
**
*****************************************************************************
*
CS
SER_CLK
SER_OUT
SER_IN
equ 0
equ 1
equ 2
equ 3
;bit # for chip select
;bit # for serial clock
;bit # for serial data out
;bit # for serial data in
*** RAM storage variables ***
OPCODE
ADDR
DATA_H
DATA_L
TEST1
TEST2
TEST3
TEST4
org RAM
rmb 1
rmb 1
rmb 1
rmb 1
rmb 1
rmb 1
rmb 1
rmb 1
;start of static RAM at $C0
;command byte
;EEPROM address byte
;MSByte of data
;LSByte of data
;test byte #1
;test byte #2
;test byte #3
;test byte #4
*****************************************************************************
*
**
* Program Initialization
*
**
* This section sets up the port for bit banging.
*
**
* To prevent floating inputs and associated high current draw,
*
* the HC705J1A has pulldown devices on all I/O pins. This
*
* initialization should enable these pulldowns on unused I/O
*
* pins. RESET_ enables the pulldowns, so no code is required.
*
**
*****************************************************************************
*
org EPROM
J9356_START lda #$80
sta PORTA
sta COPR
lda #$87
sta DDRA
;init portA
;
;kick the wdog
;init i/o of port A
AN1241/D
For More Information On This Product,
Go to: www.freescale.com
11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet AN1241.PDF ] | |
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