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The AS29LV400 is an 4 megabit, 3.0 volt Flash memory organized as 512Kbyte of 8 bits/256Kbytes of 16 bits each. For flexible
Erase and Program capability, the 4 megabits of data is divided into eleven sectors: one 16K, two 8K, one 32K, and seven 64k
byte sectors; or one 8K, two 4K, one 16K, and seven 32K word sectors. The ×8 data appears on DQ0–DQ7; the ×16 data appears
on DQ0–DQ15. The AS29LV400 is offered in JEDEC standard 48-pin TSOP and 44-pin SO. This device is designed to be
programmed and erased with a single 3.0V V
CC
supply. The device can also be reprogrammed in standard EPROM programmers.
The AS29LV400 offers access times of 70/80/90/120 ns, allowing 0-wait state operation of high speed microprocessors. To
eliminate bus contention the device has separate chip enable
(C E )
, write enable
(WE )
, and output enable
(O E )
controls. Word
mode (×16 output) is selected by
B YT E
= high. Byte mode (×8 output) is selected by
BY TE
= low.
The AS29LV400 is fully compatible with the JEDEC single power supply Flash standard. The device uses standard microprocessor
write timings to send Write commands to the register. An internal state-machine uses register contents to control the erase and
programming circuitry. Write cycles also internally latch addresses and data needed for the Programming and Erase operations.
Data is read in the same manner as other Flash or EPROM devices. Use the Program command sequence to invoke the on-chip
programming algorithm that automatically times the program pulse widths, and verifies proper cell margin. Use the Erase
command sequence to invoke the automated on-chip erase algorithm that preprograms the sector when it is not already
programmed before executing the erase operation. The Erase command also times the erase pulse widths and verifies the proper
cell margins.
Boot sector architecture enables the system to boot from either the top (AS29LV400T) or the bottom (AS29LV400B) sector.
Sector erase architecture allows specified sectors of memory to be erased and reprogrammed without altering data in other
sectors. A sector typically erases and verifies within 1.0 seconds. Hardware sector protection disables both the Program and the
Erase operations in all, or any combination of the eleven sectors. The device provides true background erase with Erase Suspend,
which puts erase operations on hold to either read data from, or program data to, a sector that is not being erased. The Chip
Erase command will automatically erase all unprotected sectors.
When shipped from the factory, AS29LV400 is fully erased (all bits = 1). The programming operation sets bits to 0. Data is
programmed into the array one byte at a time in any sequence and across sector boundaries. A sector must be erased to change
bits from 0 to 1. Erase returns all bytes in a sector to the erased state (all bits = 1). Each sector is erased individually with no
effect on other sectors.
The device features a single 3.0V power supply operation for Read, Write, and Erase functions. Internally generated and
regulated voltages are provided for the Program and Erase operations. A low V
CC
detector automatically inhibits write operations
during power transtitions. The
RY/BY
pin,
DATA
polling of DQ7, or toggle bit (DQ6) may be used to detect the end of the
program or to erase operations. The device automatically resets to the Read mode after the Program or Erase operations are
completed. DQ2 indicates which sectors are being erased.
The AS29LV400 resists accidental erasure or spurious programming signals resulting from power transitions. The Control
register architecture permits alteration of memory contents only when successful completion of specific command sequences has
occured. During power up, the device is set to Read mode with all Program/Erase commands disabled if V
CC
is less than V
LKO
(lockout voltage). The command registers are not affected by noise pulses of less than 5 ns on
O E , CE , or WE
. To initiate Write
commands,
CE
and
WE
must be a logical zero and
O E
a logical 1.
When the device’s hardware
R E S E T
pin is driven low, any Program/Erase operation in progress is terminated and the internal
state machine is reset to Read mode. If the
RE S E T
pin is tied to the system reset circuitry and a system reset occurs during an
automated on-chip Program/Erase algorithm, the operating data in the address locations may become corrupted and require
rewriting. Resetting the device enables the system’s microprocessor to read boot-up firmware from the Flash memory.
The AS29LV400 uses Fowler-Nordheim tunnelling to electrically erase all bits within a sector simultaneously. Bytes are
programmed one at a time using the EPROM programming mechanism of hot electron injection.
9/26/01; V.0.9.9.2
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ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
