Device operation

M27V322

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2.4

System considerations

The power switching characteristics of Advanced CMOS EPROMs require careful

decoupling of the supplies to the devices. The supply current ICC has three segments of

importance to the system designer: the standby current, the active current and the transient

peaks that are produced by the falling and rising edges of E. The magnitude of the transient

current peaks is dependent on the capacitive and inductive loading of the device outputs.

The associated transient voltage peaks can be suppressed by complying with the two line

output control and by properly selected decoupling capacitors. It is recommended that a

high frequency type of low inherent inductance and should be placed as close as possible to

for every eight devices. This capacitor should be mounted near the power supply connection

point. The purpose of this capacitor is to overcome the voltage drop caused by the inductive

effects of PCB traces.

2.5

Programming

When delivered (and after each erasure for UV EPROM), all bits of the M27V322 are in the

"1" state. Data is introduced by selectively programming "0"s into the desired bit locations.

Although only "0"s will be programmed, both "1"s and "0"s can be present in the data word.

The only way to change a "0" to a "1" is by die exposition to ultraviolet light (UV EPROM).

be 6.25V ± 0.25V.

2.6

PRESTO III programming algorithm

The PRESTO III Programming Algorithm allows the whole array to be programed with a

guaranteed margin in a typical time of 100 seconds. Programming with PRESTO III consists

of applying a sequence of 50µs program pulses to each word until a correct verify occurs

(see Figure 3). During programing and verify operation a MARGIN MODE circuit must be

activated to guarantee that each cell is programed with enough margin. No overprogram

pulse is applied since the verify in MARGIN MODE provides the necessary margin to each

programmed cell.