M29W640FT Datasheet, PDF (18/71 Pages) STMicroelectronics – 64 Mbit (8Mb x8 or 4Mb x16, Page, Boot Block) 3V Supply Flash Memory

Command interface
4
Command interface
M29W640FT, M29W640FB
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 6, or Table 7, depending on the configuration that is being
used, for a summary of the commands.
4.1
4.1.1
4.1.2
Standard commands
Read/Reset command
The Read/Reset command returns the memory to its Read mode. 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.
The Read/Reset command can be issued, between Bus Write cycles before the start of a
program or erase operation, to return the device to read mode. If the Read/Reset command
is issued during the timeout of a Block Erase operation then the memory will take up to 10µs
to abort. During the abort period no valid data can be read from the memory. The
Read/Reset command will not abort an Erase operation when issued while in Erase
Suspend.
Auto Select command
The Auto Select command is used to read the Manufacturer Code, the Device Code, the
Block Protection Status and the Extended Memory Block Verify Code. 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 a Read/Reset command
is issued. Read CFI Query and Read/Reset commands are accepted in Auto Select mode,
all other commands are ignored.
In Auto Select mode, the Manufacturer Code and the Device Code can be read by using a
Bus Read operation with addresses and control signals set as shown in Table 4: Bus
operations, BYTE = V_IL and Table 5: Bus operations, BYTE = V_IH, except for A9 that is ‘Don’t
Care’.
The Block Protection Status of each block can be read using a Bus Read operation with
addresses and control signals set as shown in Table 4: Bus operations, BYTE = V_IL and
Table 5: Bus operations, BYTE = V_IH, except for A9 that is ‘Don’t Care’. If the addressed
block is protected then 01h is output on Data Inputs/Outputs DQ0-DQ7, otherwise 00h is
output (in 8-bit mode).
The protection status of the Extended Memory block, or Extended Memory Block Verify
code, can be read using a Bus Read operation with addresses and control signals set as
shown in Table 4: Bus operations, BYTE = V_IL and Table 5: Bus operations, BYTE = V_IH,
except for A9 that is ‘Don’t Care’. If the Extended Block is "Factory Locked" then 80h is
output on Data Input/Outputs DQ0-DQ7, otherwise 00h is output (8-bit mode).
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