Device operation

M27W512

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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 M27W512 due to several design innovations described in the M27W512

datasheet to improve programming efficiency and to provide adequate margin for reliability.

Before starting the programming the internal MARGIN MODE circuit must be set in order to

guarantee that each cell is programmed with enough margin. Then a sequence of 100µs

program pulses is applied to each byte until a correct verify occurs (see Figure 3). No

3.6V, provides the necessary margin.

2.7

Program inhibit

Programming of multiple devices in parallel with different data is also easily accomplished.

A high level E input inhibits the other M27W512 from being programmed.

2.8

Program verify

A verify (read) should be performed on the programmed bits to determine that they were

2.9

Electronic signature

The Electronic Signature (ES) 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. The ES mode is functional in the 25°C ± 5°C

ambient temperature range that is required when programming the M27W512. To activate

the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of

the M27W512. Two identifier bytes may then be sequenced from the device outputs by

identifier bytes are given in Table 3 and can be read-out on outputs Q7 to Q0.

Note that the M27W512 and M27C512 have the same identifier byte.