M29F400 Ver la hoja de datos (PDF) - STMicroelectronics

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componentes Descripción

Fabricante

M29F400

4 Mbit (512Kb x8 or 256Kb x16, Boot Block) single supply Flash memory

STMicroelectronics 

Command interface

4

Command interface

M29F400BT, M29F400BB

All Bus Write operations to the memory are interpreted by the Command Interface.

Commands consist of one or more sequential Bus Write operations. Failure to observe a

valid sequence of Bus Write operations will result in the memory returning to Read mode.

The long command sequences are imposed to maximize data security.

The address used for the commands changes depending on whether the memory is in 16-

bit or 8-bit mode. See either Table 4., or Table 5., depending on the configuration that is

being used, for a summary of the commands.

4.1

Read/Reset command

The Read/Reset command returns the memory to its Read mode where it behaves like a

ROM or EPROM. It also resets the errors in the Status Register. Either one or three Bus

Write operations can be used to issue the Read/Reset command.

If the Read/Reset command is issued during a Block Erase operation or following a

Programming or Erase error then the memory will take upto 10µs to abort. During the abort

period no valid data can be read from the memory. Issuing a Read/Reset command during a

Block Erase operation will leave invalid data in the memory.

4.2

Auto Select command

The Auto Select command is used to read the Manufacturer Code, the Device Code and the

Block Protection Status. Three consecutive Bus Write operations are required to issue the

Auto Select command. Once the Auto Select command is issued the memory remains in

Auto Select mode until another command is issued.

From the Auto Select mode the Manufacturer Code can be read using a Bus Read operation

with A0 = VIL and A1 = VIL. The other address bits may be set to either VIL or VIH. The

Manufacturer Code for STMicroelectronics is 0020h.

The Device Code can be read using a Bus Read operation with A0 = VIH and A1 = VIL. The

other address bits may be set to either VIL or VIH. The Device Code for the M29F400BT is

00D5h and for the M29F400BB is 00D6h.

The Block Protection Status of each block can be read using a Bus Read operation with A0

= VIL, A1 = VIH, and A12-A17 specifying the address of the block. The other address bits

may be set to either VIL or VIH. If the addressed block is protected then 01h is output on

Data Inputs/Outputs DQ0-DQ7, otherwise 00h is output.

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