memory products - Al Kossow's Bitsavers

M2764ADEVICE OPERATION (Continued)The,entire seque~ce of program pulses and byteverificatipns is performed at Vcc = 6V andVpp=12.5V. When the Fast Programming cyclehas been completed, all bytes should be comparedto the original datawith Vcc=Vpp=5V. ' .PROGRAM INHIBIT,Programming of multiple M2764~s in parallel withdifferent data is also easily acc~lished. Exceptfor rn:, all like inputs (including OE) of the, parallelM2764A may be common. A TTL low pulse appliedto a M2764A's rn: input, with Vpdt 12.5V, willprogram that M2764A. A high level CE input inhibitsthe other M2764A from being programmed.PROGRAM VERIFYA verify should be performed on the programmedbits to determine that they were correC!!Jyprogrammed. The vrlfy is accomplished with OEat V'L, rn: at V'L, P M at V'H and Vpp at 12.5V.ELECTRONIC., SIGNATUREThe Electronic Signature mode allows the readingout of a binary code from an EPROM that will iden~tify its manUfacturer and type. This mode is intendedfor use by programming equipment for the purposeof automatically matching the device to beprogrammed with its corresponding programmingalgorithm. This mope is functional in the 25°C:l:.5 d C ambient ternperature,Jange that is requiredwhen programming the M2764A. To activate thismode, the programming equipment must force11 ,5V to 12.5V on address line A9 (pin 24) of theM2764A. Two identifier bytes may than be sequen-ced from the device outputs by toggling addressline AO (pin 10) from V'L to V'H' AU other addresslines must be held at V'L during Electronic Signaturemode. Byte 0 (AO = V,J represents the manufacturercode and byte 1 (AO = V,w the device identifiercode. For the SGS-THOMSON M2764A, thesetwo identifier bytes are given below. All identifiersfor manufacturer and device codes will possess oddparity, with the MSB (07) defined as the parity bit.ERASURE OPERATIONThe erasure characteristiC of the M2764A is suchthat erasure begins when the cells are exposed tolight with wavelengths shorter than approximately4000 Angstrom A. It should be noted that sunlightand some type of fluorescent lamps havewavelengths in the 3QOO.4O()() A range. Data showsthat constant exposure to room level fluorescentlighting could erase a typical M2764A in about 3years, while it would take approximately 1 week tocause erasure when expose to direct sunlight. Ifthe M2764A is to be exposed to these type of lightingconditions for extended periods of time, it issuggested that opaque labels be put over theM2764A window to prevent unintentional erasure.The recommended erasure procedure for theM2764A is exposure to short wave ultraviolet lightwhich has wavelength 2537 A. The integrated dose(Le. UV intensity x exposure time) for, erasureshould be a minimum of 15 W-sec/cm2. Theerasure time with this dosage is approximately 15to 20 minutes using an ultraviolet lamp with 12000uW/cm2 power rating. The M2764A should beplaced within 2.5 cm (1 inch) of the lamp tubes duringthe erasure. Some lamps have a filter on theirtubes which should be removed before erasure.ELECTRONIC SIGNATURE MODE~sIDENTIFIER, 'AO, 07 06(10) .. (19) .. (18)MANUFACTURER CODE V'L 0 0OEVICE CODE V'H' 0 0,05 04 03 02 01 00 Hex(17) (16) (15) (13) . , (12) (11) Da ..1 0 0 0 0 0 200 0 1 ,0 0 0 086/1048