M29KW032E datasheet(8/30 Pages) STMICROELECTRONICS

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M29KW032E

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BUS OPERATIONS

There are six standard bus operations that control

the device. These are Bus Read, Bus Write, Out-

put Disable, Standby, Automatic Standby and

Electronic Signature. See Tables 3, Bus Opera-

tions, for a summary. Typically glitches of less

than 5ns on Chip Enable or Write Enable are ig-

nored by the memory and do not affect bus opera-

tions.

Bus Read. Bus Read operations read from the

memory cells, or specific registers in the Com-

mand Interface. A valid Bus Read operation in-

volves setting the desired address on the Address

Inputs, applying a Low signal, VIL, to Chip Enable

and Output Enable and keeping Write Enable

High, VIH. The Data Inputs/Outputs will output the

value, see Figure 10, Read Mode AC Waveforms,

and Table 13, Read AC Characteristics, for details

of when the output becomes valid.

Bus Write. Bus Write operations write to the

Command Interface. A valid Bus Write operation

begins by setting the desired address on the Ad-

dress Inputs. The Address Inputs are latched by

the Command Interface on the falling edge of Chip

Enable or Write Enable, whichever occurs last.

The Data Inputs/Outputs are latched by the Com-

mand Interface on the rising edge of Chip Enable

or Write Enable, whichever occurs first. Output En-

able must remain High, VIH, during the whole Bus

Write operation. See Figures 11 and 12, Write AC

Waveforms, and Tables 14 and 15, Write AC

Characteristics, for details of the timing require-

ments.

Output Disable. The Data Inputs/Outputs are in

the high impedance state when Output Enable is

High, VIH.

Standby. When Chip Enable is High, VIH, the

memory enters Standby mode and the Data In-

puts/Outputs pins are placed in the high-imped-

ance state. To reduce the Supply Current to the

Standby Supply Current, ICC2, Chip Enable should

be held within VCC ± 0.2V. For the Standby current

level see Table 12, DC Characteristics.

During program or erase operations the memory

will continue to use the Program/Erase Supply

Current, ICC3, for Program or Erase operations un-

til the operation completes.

Automatic Standby. If CMOS levels (VCC ± 0.2V)

are used to drive the bus and the bus is inactive for

150ns or more the memory enters Automatic

Standby where the internal Supply Current is re-

duced to the Standby Supply Current, ICC2. The

Data Inputs/Outputs will still output data if a Bus

Read operation is in progress.

Electronic Signature. The

memory

has

two

codes, the manufacturer code and the device

code, that can be read to identify the memory.

These codes can be read by applying the signals

listed in Tables 3, Bus Operations.

Table 3. Bus Operations

Note: 1. X = VIL or VIH.

2. XX = VIL , VIH or VHH

3. Not necessary for Auto Select or Read/Reset commands.

4. When reading the Status Register during Program or Erase operations, VPP must be kept at VHH.

Operation

VPP

Address Inputs

A0-A20

Data Inputs/Outputs

DQ15-DQ0

Bus Read

VIL

VIH

XX(4)

Cell Address

Data Output

Bus Write

VIL

VIH

VIL

VHH

(3)

Command Address

Data Input

Output Disable

VIH

Hi-Z

Standby

VIH

Hi-Z

Read Manufacturer

Code

VIL

VIH

A0 = VIL, A1 = VIL,

Others VIL or VIH

0020h

Read Device Code

VIL

VIH

A0 = VIH, A1 = VIL,

Others VIL or VIH

88ACh

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