M29F400BT datasheet(14/40 Pages) STMICROELECTRONICS

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Bus operations

M29F400BT, M29F400BB

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3.5

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 reduced to

the CMOS Standby Supply Current, ICC3. The Data Inputs/Outputs will still output data if a

Bus Read operation is in progress.

3.6

Special bus operations

Additional bus operations can be performed to read the Electronic Signature and also to

apply and remove Block Protection. These bus operations are intended for use by

programming equipment and are not usually used in applications. They require VID to be

applied to some pins.

3.6.1

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 Table 2.

and Table 3., Bus Operations.

3.6.2

Block Protection and Blocks Unprotection

Each block can be separately protected against accidental Program or Erase. Protected

blocks can be unprotected to allow data to be changed.

There are two methods available for protecting and unprotecting the blocks, one for use on

programming equipment and the other for in-system use. For further information refer to

Application Note AN1122, Applying Protection and Unprotection to M29 Series Flash.

Table 2.

Bus operations, BYTE = VIL

(1)

X = VIL or VIH.

Operation

Address Inputs

DQ15A–1, A0-A17

Data Inputs/Outputs

DQ14-DQ8

DQ7-DQ0

Bus Read

VIL

VIH Cell Address

Hi-Z

Data Output

Bus Write

VIL

VIH

VIL Command Address

Hi-Z

Data Input

Output Disable

VIH

VIH X

Hi-Z

Standby

VIH

Hi-Z

Read Manufacturer

Code

VIL

VIH

A0 = VIL, A1 = VIL, A9

= VID, Others VIL or VIH

Hi-Z

20h

Read Device Code

VIL

VIH

A0 = VIH, A1 = VIL, A9

= VID, Others VIL or VIH

Hi-Z

D5h (M29F400BT)

D6h (M29F400BB)

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