MB90233 Просмотр технического описания (PDF) - Fujitsu

Номер в каталоге

Компоненты Описание

Список матч

MB90233

16-bit Proprietary Microcontroller

Fujitsu 

MB90230 Series

8. Program Mode

When shipped from Fujitsu, and after each erasure, all bits (96K × 8 bits) in the MB90W234 and MB90P234 are

in the “1” state. Data is introduced by selectively programming “0’s” into the desired bit locations. Bits cannot

be set to 1 electrically.

9. Erasure Procedure

Data written in the MB90W234 is erased (from 0 to 1) by exposing the chip to ultraviolet rays with a wavelength

of 2,537Å through the translucent cover.

Recommended irradiation dosage for exposure is 10 Wsec/cm2. This amount is reached in 15 to 20 minutes

with a commercial ultraviolet lamp positioned 2 to 3 cm above the package (when the package surface

illuminance is 1200 µW/cm2).

If the ultraviolet lamp has a filter, remove the filter before exposure. Attaching a mirrored plate to the lamp

increases the illuminance by a factor of 1.4 to 1.8, thus shortening the required erasure time. If the translucent

part of the package is stained with oil or adhesive, transmission of ultraviolet rays is degraded, resulting in a

longer erasure time. In that case, clean the translucent part using alcohol (or other solvent not affecting the

package).

The above recommended dosage is a value which takes the guard band into consideration and is a multiple of

the time in which all bits can be evaluated to have been erased. Observe the recommended dosage for erasure;

the purpose of the guard band is to ensure erasure in all temperature and supply voltage ranges. In addition,

check the lifespan of the lamp and control the illuminance appropriately.

Data in the MB90W234 is erased by exposure to light with a wavelength of 4000Å or less.

Data in the device is also erased even by exposure to fluorescent lamp light or sunlight although the exposure

results in a much lower erasure rate than exposure to 2537Å ultraviolet rays. Note that exposure to such lights

for an extended period will therefore affect system reliability. If the chip is used where it is exposed to any light

with a wavelength of 4000Å or less, cover the translucent part, for example, with a protective seal to prevent

the chip from being exposed to the light.

Exposure to light with a wavelength of 4,000 to 5,000Å or more will not erase data in the device. If the light

applied to the chip has a very high illuminance, however, the device may cause malfunction in the circuit for

reasons of general semiconductor characteristics. Although the circuit will recover normal operation when

exposure is stopped, the device requires proper countermeasures for use in a place exposed continuously to

such light even though the wavelength is 4,000Å or more.

16

Share Link: