M27C322_06 datasheet(7/24 Pages) STMICROELECTRONICS

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M27C322

Device operation

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Device operation

The operating modes of the M27C322 are listed in the Operating Modes Table. A single

power supply is required in the read mode. All inputs are TTL compatible except for VPP and

12V on A9 for the Electronic Signature.

2.1

Read mode

The M27C322 has a word-wide organization. Chip Enable (E) is the power control and

should be used for device selection. Output Enable (G) is the output control and should be

used to gate data to the output pins independent of device selection. Assuming that the

addresses are stable, the address access time (tAVQV) is equal to the delay from E to output

(tELQV). Data is available at the output after a delay of tGLQV from the falling edge of GVPP,

assuming that E has been low and the addresses have been stable for at least tAVQV-tGLQV.

2.2

Standby mode

The M27C322 has a standby mode which reduces the supply current from 50mA to 100µA.

The M27C322 is placed in the standby mode by applying a CMOS high signal to the E

input.When in the standby mode, the outputs are in a high impedance state, independent of

the GVPP input.

2.3

Two line output control

Because EPROMs are usually used in larger memory arrays, this product features a 2 line

control function which accommodates the use of multiple memory connection. The two line

control function allows:

the lowest possible memory power dissipation,

complete assurance that output bus contention will not occur.

For the most efficient use of these two control lines, E should be decoded and used as the

primary device selecting function, while GVPP should be made a common connection to all

devices in the array and connected to the READ line from the system control bus. This

ensures that all deselected memory devices are in their low power standby mode and that

the output pins are only active when data is required from a particular memory device.

M27C322 Datasheet(PDF) 7 Page - STMicroelectronics