®
AS29LV400
January 2001
Alliance Semiconductor 2
Functional description
The AS29LV400 is an 4 megabit, 3.0 volt only Flash memory organized as 512Kbyte of 8 bits/256Kbytes of 16 bits each. For
flexible era se and p rogram cap ability, the 4 megabits of data i s divide d into eleven sectors: o ne 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 AS29L V 400 is off ere d in JED EC stand ard 48-p in T SOP and 44-pin SOP packa g es. This device
is designed to be progra mmed a nd e ras ed in-s ys tem wit h a sin gl e 3.0 V V
CC
supply. The device can al so be re progr ammed in
standard EPROM programmers.
The AS29LV400 offers access times of 80/90/120 ns, allowing 0-wait state operation of high speed microprocessors. To
eliminate bus contention the device has separate chip enable (CE
), write e nable (WE), and output enable (OE) controls. Word
mode (×16 output) is selected by BYTE
= high and Byte mode (×8 output) is selected by BYTE = low.
The AS29LV400 is fully compatible with the JEDEC single power supply Flash standard. Write commands to the command
register using st anda rd mi cr oprocessor write timings. An inter nal stat e-m achine uses re gist er co nte nts t o control the erase and
programming ci rcuitry. Write cycles also internally latch add resses and data needed for the programming and erase operations.
Read data from t he device in the sam e manner as other Fla sh or EPROM devices. Use the progr am command sequen ce to
invoke the automated on-chip progra mming 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 if
it is not already programmed before executing the erase operation, times the erase pulse widths, and verifies proper cell
margin.
Boot sector architecture enables the system to boot from either the top (AS29LV400T) or the bottom (AS29LV400B) sector.
Sector erase architec ture allows specifie d sectors of mem ory to be era sed and reprogra mmed without al tering data in other
sectors. A sect or typic al ly erases an d ver ifies wit h in 1.0 seconds. Hardware sector protection disables both program and erase
operations in all or a ny combination of the eleven sectors. The device provides tru e background erase wit h Erase Suspend,
which p uts erase operation s on h old to e ither read data from or prog ram data t o a se ctor th at is not being erased. The c hip
erase command will automatically erase all unprotected sectors.
A factory shipped AS29LV400 is fully erased (all bits = 1). The programming operation sets bits to 0. Data is programmed into
the array on e byte at a time i n 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 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 end of program or erase
operations. The device automatically resets t o the read mode after p rogram/erase operation s are completed. DQ2 indicates
which sectors are being erased.
The AS29LV400 resists accidental erasure or spurious programming signals resulting from power transitions. Control register
architecture permits alteration of memory contents only after successful completion of specific command sequences. During
power up, the device is s et to rea d mode with all prog ram/erase com mands dis abled when V
CC
is les s than V
LKO
(lockout
voltage). The command registers are not affected by noise pulses of less than 5 ns on OE
, CE, or WE. To initiate wr ite
commands, CE
and WE must be logical zero and OE a logical one.
When the device’s hardware R ES ET
pin is driven low, any program/erase operati on in progress is ter mi nated and th e int er nal
state mach ine is reset to read mode. If the RESET
pin is tied to the system reset circuitry and a system reset occurs during an
automated on-chip program/erase algorithm, data in address locations being operated on may become corrupted and requires
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 usin g EPROM progr amming mechanism of ho t electron injection.