M27C512

Device operation

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Figure 4.

Programming flowchart

2.5

Programming

When delivered (and after each erasure for UV EPROM), all bits of the M27C512 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 exposure to ultraviolet light (UV EPROM). The

The data to be programmed is applied to 8 bits in parallel to the data output pins. The levels

M27C512 can use PRESTO IIB Programming Algorithm that drastically reduces the

programming time (typically less than 6 seconds). Nevertheless to achieve compatibility with

all programming equipments, PRESTO Programming Algorithm can be used as well.

2.6

PRESTO IIB programming algorithm

PRESTO IIB Programming Algorithm allows the whole array to be programmed with a

guaranteed margin, in a typical time of 6.5 seconds. This can be achieved with

STMicroelectronics M27C512 due to several design innovations described in the M27C512

datasheet to improve programming efficiency and to provide 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 100µs

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.

AI00738B

n = 0

Last

Addr

VERIFY

E = 100

µs Pulse

++n

= 25

++ Addr

VCC = 6.25V, VPP = 12.75V

FAIL

CHECK ALL BYTES

1st: VCC = 6V

2nd: VCC = 4.2V

YES

NO

YES

NO

YES

NO

SET MARGIN MODE

RESET MARGIN MODE