Материал: 27512

tA9HVPH tAS9

tVPHEL tVPS

tA10HEH tAS10

tA10LEH tAS10

tEXA10X tAH10

tEXVPX tVPH

tVPXA9X tAH9

VA9 High to VPP High

VPP High to Chip Enable Low

VA10 High to Chip Enable High (Set)

VA10 Low to Chip Enable High (Reset)

Chip Enable Transition to VA10 Transition

Chip Enable Transition to VPP Transition

VPP Transition to VA9

Transition

tAVEL tAS

tQVEL tDS

tVCHEL tVCS

tVPHEL tOES

tVPLVPH tPRT

tELEH tPW

tELEH tOPW

tEHQX tDH

tEHVPX tOEH

tVPLEL tVR

tELQV tDV

(4)

tEHQZ tDF

tEHAX tAH

Address Valid to Chip Enable Low

Input Valid to Chip Enable Low

VCC High to Chip Enable Low

VPP High to Chip Enable Low

VPP Rise Time

Chip Enable Program Pulse

Width (Initial)

Chip Enable Program Pulse

Width (Overprogram)

Chip Enable High to Input Transition

Chip Enable High to VPP Transition

VPP Low to Chip Enable Low

Chip Enable Low to Output Valid

Chip Enable High to Output Hi- Z

Chip Enable High to Address Transition

DEVICE OPERATION (cont'd)

The Fast Programming Algorithm utilizes two different pulse types : initial and overprogram. The duration of the initial E pulse(s) is 1ms, which will then be followedby a longer overprogrampulseof length 3ms by n (n is an iteration counter and is equal to the number of the initial one millisecond pulses applied to a particular M27512 location), before a correct verify occurs. Up to 25 one-millisecond pulses per byte are provided for before the over program pulse is applied.

The entire sequence of program pulses is performed at VCC = 6V and GVPP = 12.5V (byte verifications at VCC = 6V and GVPP = VIL). When the Fast Programming cycle has been completed, all bytes should be compared to the original data with VCC = 5V.

PRESTO Programming Algorithm

PRESTO Programming Algorithm allows to program the whole array with a guaranted margin, in a typical time of less than 50 seconds (to be compared with 283 seconds for the Fast algorithm). This can be achieved with the SGS-THOMSON M27512 due to several design innovations described in the next paragraph that improves programming efficiency and brings adequate margin

for reliability. Before starting the programming the internal MARGIN MODE circuit is set in order to guarantee that each cell is programmed with enough margin.

Then a sequence of 500μs program pulses are applied to each byte until a correct verify occurs. No overprogram pulses are applied since the verify in MARGIN MODE provides the necessary margin to each programmed cell.

Program Inhibit

Programming of multiple M27512s in parallel with different data is also easily accomplished. Except for E, all like inputs (including GVPP) of the parallel M27512 may be common. A TTL low level pulse applied to a M27512's E input, with GVpp at 12.5V, will program that M27512. A high level E input inhibits the other M27512s from being programmed.

Program Verify

A verify (read) should be performed on the programmed bits to determine that they were correctly programmed. The verify is accomplished with GVpp and E at VIL. Data should be verified tDV after the falling edge of E.

Electronic Signature

The Electronic Signature mode allows the reading out of a binary code from an EPROM that will identify its manufacturer and type. This mode is intended for use by programming equipment to automatically match the device to be programmed with its corresponding programming algorithm. This mode is functional in the 25 °C ± 5 °C ambient temperature range that is required when programming the M27512. To activate this mode, the programming equipment must force 11.5V to 12.5V on address line A9 of the M27512. Two identifier bytes may then be sequenced from the device outputs by toggling address line A0 from VIL to VIH. All other address lines must be held at VIL during Electronic Signature mode, except for A14 and A15 which should be high. Byte 0 (A0 = VIL) represents the manufacturercode and byte 1 (A0 = VIH) the device identifier code.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristic of the M27512 is such that erasure begins when the cells are exposed to

light with wavelengths shorter than approximately 4000 Å. It should be noted that sunlight and some type of fluorescent lamps have wavelengths in the 3000-4000 Å range. Research shows that constant exposure to room level fluorescent lighting could erase a typical M27512 in about 3 years, while it would take approximately 1 week to cause erasure when expose to direct sunlight. If the M27512 is to be exposed to these types of lighting conditions for extended periods of time, it is suggested that opaque labels be put over the M27512 window to prevent unintentional erasure. The recommended erasure procedure for the M27512 is exposure to short wave ultraviolet light which has wavelength 2537 Å.

The integrated dose (i.e. UV intensity x exposure time) for erasure should be a minimum of 15 W-sec/cm2. The erasure time with this dosage is approximately 15 to 20 minutes using an ultraviolet lamp with 12000 μW/cm2 power rating. The M27512 should be placed within 2.5 cm (1 inch) of the lamp tubes during the erasure. Some lamps have a filter on their tubes which should be removed before erasure.