ST52T430 datasheet(26/88 Pages) STMICROELECTRONICS

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ST52T430/E430

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3.1.4 EPROM Read/Verify Margin Mode.

The read phase is executed with VPP= 5V±5%,

instead of the verify phase that needs VPP=

12V

±5%.

The Memory Verify operation is available in order

to verify the accuracy of the data written. A

Memory Verify Margin Mode operation can be

executed immediately after writing each byte, in

this case (see Figure ):

1) a positive pulse on RST_CONF signal resets the

EPROM Control Register, if it wasn’t already reset;

2) one positive pulse on INC_CONF loads the

Memory Read/Verify operation code;

3) a negative pulse (100 ns) on the PHASE signal

validates the Memory Reading / Verify operation;

4) a negative pulse on RST_CONF signal puts in

the PA(0:7) port the value stored in the actual

memory address and resets the EPROM Control

If an error occurred writing, the user has to repeat

EPROM writing.

3.1.5 Stand by Mode.

EPROM has a standby mode, which reduces the

active current from 10mA (Programming mode) to

less than 100

µA. Memory is placed in standby

mode by setting the PHASE signal at a high level

or when the EPROM Control Register value is 0

and the PHASE signal is low.

3.1.6 ID code.

A software identification code, called ID code may

be written in order to distinguish which software

version is stored in the memory.

64 Bytes are dedicated to store this code by using

the address values from 0 to 63.

The ID Code may be read or verified even if the

Memory Lock Status is “0".

The timing signals are the same as that of a normal

operation.

3.2 Eprom Erasure

The

transparent

window

available

the

CSDIP32W package, allows the memory contents

to be erased by exposure to UV light.

Erasure begins when the device is exposed to light

with a wavelength shorter than 4000Å. Sunlight, as

well as some types of artificial light, includes

wavelengths in the 3000-4000Å range which, on

prolonged exposure can cause erasure of memory

contents. Therefore, it is recommended that

EPROM devices be fitted with an opaque label

over the window area in order to prevent

unintentional erasure.

The erasure procedure recommended for EPROM

devices consists of exposure to short wave UV

light having a wavelength of 2537Å. The minimum

integrated dose recommended (intensity x expo-

sure time) for complete erasure is 15Wsec/cm 2.

This is equivalent to an erasure time of 15-20

minutes using a UV source having an intensity of

12mW/cm 2 at a distance of 25mm (1 inch) from

the device window.

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