ST9040 datasheet(10/56 Pages) STMICROELECTRONICS

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Figure 1-4. Memory Map

1.3 MEMORY

1.3.1 INTRODUCTION

The memory of the ST9 is divided into two spaces:

- Data memory with up to 64K (65536) bytes

- Program memory with up to 64K (65536) bytes

Thus, there is a total of 128K bytes of addressable

memory space.

The 16K bytes of on-chip ROM memory of the

ST9040 are selected at memory addresses 0

through 3FFFh (hexadecimal) in the PROGRAM

space.

The DATA space includes the 512 bytes of on-chip

EEPROM at addresses 0 through 1FFh and the

256 bytes of on-chip RAM memory at addresses

200h through 2FFh.

1.3.2 EEPROM

1.3.2.1 Introduction

The EEPROMmemory provides user-programma-

ble non-volatile memory on-chip, allowing fast and

reliable storage of user data. As there is also no

off-chip access required, as for an external serial

EEPROM, high security levels can be achieved.

The EEPROM memory is read as normal RAM

memory at Data Space addresses 0 to 1FFh, how-

ever one WAIT cycle is automatically added for a

Read cycle, while a byte write cycle to the

EEPROM will cause the start of an ERASE/WRITE

cycle at the addressed location. Word (16 bit)

writes are not allowed.

The programming cycle is self-timed, with a typical

programming time of 6ms. The voltage necessary

for programming the EEPROM is internally gener-

ated with a +18V charge pump circuit.

Up to 16 bytes of data may be programmed into

the EEPROM during the same write cycle by using

the PARALLEL WRITE function.

A standby mode is also available which disables all

power consumption sources within the EEPROM

for low power requirements. When STBY is high,

any attempt to access the EEPROM memory will

produce unpredictable results. After the re-ena-

bling of the EEPROM, a delay of 6 INTCLK cycles

must be allowed before the selection of the

EEPROM.

The EEPROM of the ST9040 has been imple-

mented in a high reliability technology developed

by SGS-THOMSON, this, together with the double

bit structure, allow 300k Erase/Write cycles and 10

year data retention to be achieved on a microcon-

troller.

Control of the EEPROM is performed through one

ST9040

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