M27C64A datasheet(9/22 Pages) STMICROELECTRONICS

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M27C64A

Device operation

9/22

be a high frequency capacitor of low inherent inductance and should be placed as close to

the device as possible. In addition, a 4.7µF bulk electrolytic capacitor should be used

between VCC and VSS for every eight devices. The bulk capacitor should be located near the

power supply connection point. The purpose of the bulk 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 M27C64A 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).

The M27C64A is in the programming mode when VPP input is at 12.5V, E is at VIL and P is

pulsed to VIL. The data to be programmed is applied to 8 bits in parallel to the data output

pins. The levels required for the address and data inputs are TTL. VCC is specified to be 6V

± 0.25V.

2.6

High-speed programming

The high speed programming algorithm, described in Figure 4, rapidly programs the

M27C64A using an efficient and reliable method, particularly suited to the production

programming environment. An individual device will take around 1 minute to program.

Figure 4.

Programming Flowchart

AI01167

n = 1

Last

Addr

VERIFY

P = 1ms Pulse

++n

> 25

++ Addr

VCC = 6V, VPP = 12.5V

FAIL

CHECK ALL BYTES

1st: VCC = 6V

2nd: VCC = 4.2V

YES

P = 3ms Pulse by n

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