TMS29F400B Datasheet, PDF (11/51 Pages) Texas Instruments – 524288 BY 8-BIT/262144 BY 16-BIT FLASH MEMORIES

TMS29F400T, TMS29F400B
524288 BY 8-BIT/262144 BY 16-BIT
FLASH MEMORIES
SMJS843A – MAY 1997 – REVISED SEPTEMBER 1997
erasure and programming
Erasure and programming of the ’29F400 are accomplished by writing a sequence of commands using standard
microprocessor write timing. The commands are written to a command register and input to the command-state
machine (CSM). The CSM interprets the command entered and initiates program, erase, suspend, and resume
operations as instructed. The CSM acts as the interface between the write-state machine (WSM) and
external-chip operations. The WSM controls all voltage generation, pulse generation, preconditioning, and
verification of memory contents. Program and block-/chip-erase functions are fully automatic. Once the end of
a program or erase operation has been reached, the device resets internally to the read mode. If V_CC drops
below the low-voltage-detect level (V_LKO), any programming or erase operation is aborted and subsequent
writes are ignored until the V_CC level is greater than V_LKO. The control pins must be logically correct to prevent
unintentional command writes or programming or erasing.
command definitions
Device operating modes are selected by writing specific address and data sequences into the command
register. Table 6 defines the valid command sequences. Writing incorrect address and data values or writing
them in the incorrect sequence causes the device to reset to the read mode. The command register does not
occupy an addressable memory location. The register is used to store the command sequence, along with the
address and data needed by the memory array. Commands are written by setting CE = V_IL, OE = V_IH, and
bringing WE from logic high to logic low. Addresses are latched on the falling edge of WE and data is latched
on the rising edge of WE. Holding WE = V_IL and toggling CE is an alternative method. See the switching
characteristics of the write/erase/program-operations section for specific timing information.
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