M29W400T Datasheet, PDF (6/34 Pages) STMicroelectronics – 4 Mbit 512Kb x8 or 256Kb x16, Boot Block Low Voltage Single Supply Flash Memory

M29W400T, M29W400B
Command Interface
Instructions, made up of commands written in cy-
cles, can be given to the Program/Erase Controller
through a Command Interface (C.I.). For added
data protection, program or erase execution starts
after 4 or 6 cycles. The first, second, fourth and fifth
cycles are used to input Coded cycles to the C.I.
This Coded sequence is the same for all Pro-
gram/Erase Controller instructions. The ’Com-
mand’ itself and its confirmation, when applicable,
are given on the third, fourth or sixth cycles. Any
incorrect command or any improper command se-
quence will reset the device to Read Array mode.
Instructions
Seven instructions are defined to perform Read
Array, Auto Select (to read the ElectronicSignature
or Block Protection Status), Program, Block Erase,
Chip Erase, Erase Suspend and Erase Resume.
The internal P/E.C. automatically handles all tim-
ing and verification of the Program and Erase
operations. The Status Register Data Polling, Tog-
gle, Error bits and the RB output may be read at
any time, during programming or erase, to monitor
the progress of the operation.
Instructions are composed of up to six cycles. The
first two cycles input a Coded sequence to the
Command Interfacewhich is common to all instruc-
tions (see Table 8). The third cycle inputs the
instruction set-up command. Subsequent cycles
output the addressed data, Electronic Signature or
Block Protection Status for Read operations. In
order to give additionaldata protection,the instruc-
tions for Program and Block or Chip Erase require
furthercommand inputs. For a Programinstruction,
the fourth command cycle inputs the address and
data to be programmed. For an Erase instruction
(Block or Chip), the fourth and fifth cycles input a
further Coded sequence before the Erase confirm
command on the sixth cycle. Erasure of a memory
block may be suspended,in order to read data from
another block or to program data in another block,
and then resumed.
When power is first applied or if VCC falls below
VLKO, the command interface is reset to Read
Array.
SIGNAL DESCRIPTIONS
See Figure 1 and Table 1.
Address Inputs (A0-A17). The address inputs for
the memory array are latched during a write opera-
tion on the falling edge of Chip Enable E or Write
Enable W. In Word-wide organisation the address
lines are A0-A17, in Byte-wide organisation
DQ15A–1 acts as an additional LSB address line.
When A9 is raised to V_ID, either a Read Electronic
Signature Manufacturer or Device Code, Block
Protection Status or a Write Block Protection or
Block Unprotection is enabled depending on the
combination of levels on A0, A1, A6, A12 and A15.
Data Input/Outputs (DQ0-DQ7). T h e se I n-
puts/Outputs are used in the Byte-wide and Word-
wide organisations. The input is data to be
programmed in the memory array or a command
to be written to the C.I. Both are latched on the
rising edge of Chip Enable E or Write Enable W.
The output is data from the Memory Array, the
Electronic Signature Manufacturer or Device
codes, the Block Protection Status or the Status
register Data Polling bit DQ7, the Toggle Bits DQ6
and DQ2, the Error bit DQ5 or the Erase Timer bit
DQ3. Outputs are valid when Chip Enable E and
Output Enable G are active. The output is high
impedance when the chip is deselected or the
outputs are disabled and when RP is at a Low level.
Data Input/Outputs (DQ8-DQ14 and DQ15A–1).
These Inputs/Outputs are additionally used in the
Word-wide organisation.When BYTEis High DQ8-
DQ14 and DQ15A–1 act as the MSB of the Data
Input or Output, functioning as described for DQ0-
DQ7 above, and DQ8-DQ15 are ’don’t care’ for
command inputs or status outputs. When BYTE is
Low, DQ8-DQ14 are high impedance, DQ15A–1 is
the Address A–1 input.
Chip Enable (E). The Chip Enable input activates
the memory control logic, input buffers, decoders
and sense amplifiers. E Highdeselects the memory
and reduces the power consumptionto the standby
level. E can also be used to control writing to the
command register and to the memory array, while
W remains at a low level. The Chip Enable must be
forced to VID during the Block Unprotection opera-
tion.
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