M28C64 datasheet(7/24 Pages) STMICROELECTRONICS

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M28C64

Table 5. Chip Erase AC Characteristics1 for M28C64 and M28C64-xxW

(TA = 0 to 70 °C or –40 to 85 °C or –40 to 125 °C; VCC = 4.5 to 5.5 V)

(TA = 0 to 70 °C or –40 to 85 °C; VCC = 2.7 to 3.6 V)

Note: 1. Sampled only, not 100% tested.

Symbol

Parameter

Test Condition

Min.

Max.

Unit

tELWL

Chip Enable Low to Write Enable Low

G= VCC +7V

µs

tWHEH

Write Enable High to Chip Enable High

G = VCC +7V

tWLWH2

Write Enable Low to Write Enable High

G= VCC +7V

tGLWH

Output Enable Low to Write Enable High

G= VCC +7V

µs

tWHRH

Write Enable High to Write Enable Low

G = VCC +7V

throughout this write operation: it is inverted while

the internal write operation is underway, and is

inverted back to its original value once the

operation is complete.

Toggle bit (DQ6). The device offers another way

for determining when the internal write cycle is

completed. During the internal Erase/Write cycle,

DQ6 toggles from ’0’ to ’1’ and ’1’ to ’0’ (the first

read value being ’0’) on subsequent attempts to

read any byte of the memory. When the internal

write cycle is complete, the toggling is stopped,

and the values read on DQ7-DQ0 are those of the

addressed memory byte. This indicates that the

device is again available for new Read and Write

operations.

Page Load Timer Status bit (DQ5). An internal

timer is used to measure the period between

successive

Write

operations,

tWLQ5H

(defined in Table 10A to Table 10C). The DQ5 line

is held low to show when this timer is running

(hence showing that the device has received one

write operation, and is waiting for the next). The

DQ5 line is held high when the counter has

overflowed (hence showing that the device is now

starting the internal write to the memory array).

Ready/Busy pin. The RB pin is an open drain

output that is held low during the erase/write cycle,

and that is released (allowed to float) at the

completion of the programming cycle.

Figure 7. Chip Erase AC Waveforms (M28C64 and M28C64-xxW)

AI01484B

tWLWH2

tELWL

tGLWH

tWHRH

tWHEH

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