Intel mcs-48 manual Family, Waveforms

2708 FAMILY

A.C. WAVEFORMS 121

ADDRESSES	ADDRESSES
	VALID

CS/WE

~--- teo I'II---~

I----+--tACC (31 -------	1
OUTPUT _____...:.:.HI:;;:G:.:.H,:,Z____-f+~H~+_~H++_t_<

NOTES:

2.ALL TIMES SHOWN IN PARENTHESES ARE MINIMUM AND ARE NSEC UNLESS OTHERWISE SPECIFIED.

3.CS MAY BE DELAYED UP TO tACC·tCO AFTER ADDRESSES ARE VALID

K

V

tOF (4)

toH

(a)

VALID OUTPUT ~ HIGH Z

~//

4.~1;7~~~~~I~~iri~R'6::~'OR ADDRESS CHANGE, WHICHEVER OCCURS FIRST.

ERASURE CHARACTERISTICS

The erasure characteristics of the 2708 family are such that erasure begins to occur when exposed to light with wave- lengths shorter than approximately 4000 Angstroms (A). It should be noted that sunlight and certain types of fluores- cent lamps have wavelengths in the 3000-4000Arange. Data show that constant exposure to room level fluores- cent lighting could erase the typical device in approxi- mately 3 years, while it would take approximately 1 week to cause erasure when exposed to direct sunlight. If the 2708 is to be exposed to these types of lighting conditions for extended periods of time, opaque labels are available from Intel which should be placed over the 2708 window to prevent unintentional erasure.

The recommended erasure procedure (see Data Catalog PROM/ROM Programming Instructions Section) for the 2708 family is exposure to shortwave ultraviolet light which has a wavelength of 2537 Angstroms (A). The inte- grated dose (j,e" UV intensity X exposure time) for erasure should be a minimum of 15 W-sec/cm 2. The erasure time with this dosage is approximately 15 to 20 minutes using an ultraviolet lamp with a 12000 /J.W/cm 2 power rating, The device should be placed within 1 inch of the lamp tubes during erasure, Some lamps have a filter on their tubes which should be removed before erasure,

8-11 AFN-01104A-04