Warning: compatibility with FLASH Memory

Compatibility issues may arise when replacing the

compatible Single Supply 4 Megabit FLASH Mem-

ory (the M29F040) by the M27C405.

withstand voltages up to 12.75V, while the ”W” pin

of the M29F040 is a normal control signal input and

may be damaged if a high voltage is applied;

special precautions must be taken when program-

ming in-circuit.

However if an already programmed M27C405 is

used, this can be directly put in place of the FLASH

Changes to PRESTO II. The duration of the pro-

gramming pulse is reduced to 20

µs, making the

programming time of the M27C405 comparable

with the counterpart FLASH Memory.

Electronic Signature

The Electronic Signature (ES) mode allows the

reading out of a binary code from an OTP EPROM

that will identify its manufacturer and type. this

mode is intended for use by programming equip-

ment to automatically match the device to be pro-

grammed with its corresponding programming

algorithm. This mode is functionalin the 25

°C ± 5°C

ambient temperature range that is required when

programming the M27C405. To activate the ES

mode, the programming equipment must force

11.5V to 12.5V on address line A9 of the M27C405

sequenced from the device outputs by toggling

identifier code. For the STMicroelectronics

M27C405, these two identifier bytes are given in

Table 4 and can be read-out on outputs Q0 to Q7.

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M27C405