Device operation

M27C4001

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2

Device operation

The operating modes of the M27C4001 are listed in the Operating Modes table. A single

on A9 for Electronic Signature.

2.1

Read Mode

The M27C4001 has two control functions, both of which must be logically active in order to

obtain data at the outputs. 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,

2.2

Standby Mode

The M27C4001 has a standby mode which reduces the supply current from 30mA to 100

µA.

The M27C4001 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 G 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:

a)

the lowest possible memory power dissipation,

b)

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 G 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.