Intel mcs-48 manual Single Component System

SINGLE COMPONENT SYSTEM

+5V
RESET
O------------	~--~
+5V---....,	--- BUS AND PROG CAN BE DRIVEN ONLY DURING THIS TIME - I1--------
TEST 0

o

+23V

EA

+5V ____---I

BUS

P20·21PREVIOUS ADDRESS

+25V

VDD

(

X

ADDRESS AO-A7	X DATA	>	<DATA OUT
ADDRESS A8-A9

+5V -----------------------------------------	I
FLOAT	+23V I	'--__--	FLOAT
PROG +OV - - -- ,'	---1		i' - - -- - - -

SEE 8048/8748 DATA SHEET (CHAPTER 6) FOR DETAIL TIMING SPECIFICATIONS.

WARNING: An attempt to program a mis-socketed 8748 will result in severe damage to the part. An indication of a properly socketed part is the appearance of the ALE clock output. The lack of this clock may be used to disable the programmer.

PROGRAMMINGIVERIFY. SEQUENCE

8748 Erasure Characteristics

The erasure characteristics of the 8748 are such that erasure begins to occur when exposed to light with wavelengths sh<6rter than approximately 4000 Angstroms (Al. It should be noted that sunlight and certain types of fluorescent lamRs have wave- lengths in the 3000-4000A range. Data show that constant exposure to room level fluorescent lighting could erase the typical 8748 in approximately 3 years while it would take approximately 1 week to cause erasure when exposed to direct sunlight. If the 8748 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 8748 win- dow to prevent unintentional erasure.

When erased, bits of the 8748 Program Memory are in the logic "0" state.

The recommended erasure procedure for the 8748 is exposure to shortwave ultra- violet light which has a wavelength of 2537 Angstroms tAl. The integrated dose (i.e., UV intensity X exposure time) for erasure should be a minimum of 15W-sec/cm2. The erasure time with this dosage is approxi- mately 15 to 20 minutes using an ultraviolet lamp with a 12000jlW/cm 2 power rating. The 8748 should be placed within one inch from the lamp tubes during erasure. Some lamps have a filter on their tubes and this filter should be removed before erasure.

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