P R E L I M I N A R Y
ing them in the improper sequence will reset the
Write
device to the read mode. Table 5 on page 13 defines
the valid register command sequences. Note that the
Erase Suspend (B0H) and Erase Resume (30H) com-
mands are valid only while the Sector Erase operation
is in progress.
Device erasure and programming are accomplished
via the command register. The command register is
written by bringing WE to V , while CE is at V and OE
IL
IL
is at V . Addresses are latched on the falling edge of
IH
CE or WE, whichever occurs later, while data is latched
on the rising edge of the CE or WE pulse, whichever
occurs first. Standard microprocessor write timings are
used.
Read/Reset Command
The device will automatically power up in the read/
reset state. In this case, a command sequence is
not required to read data. Standard microproces-
sor cycles will retrieve array data. This default
value ensures that no spurious alteration of the
memory content occurs during the power transi-
tion. Refer to the AC Characteristics section for the
specific timing parameters.
Refer to AC Write Characteristics and the Erase/
Programming Waveforms for specific timing parameters.
Sector Protection
Sectors of the Am29LV008 may be hardware protected
at the user’s factory with external programming equip-
ment.The protection circuitry will disable both program
and erase functions for the protected sectors, making
the protected sectors read-only. Requests to program
or erase a protected sector will be ignored by the de-
vice. If the user attempts to write to a protected sector,
DATA Polling will be activated for about 1 µs; the device
will then return to read mode, with data from the pro-
tected sector unchanged. If the user attempts to erase
a protected sector, Toggle Bit will be activated for about
50 µs; the device will then return to read mode, without
having erased the protected sector.
The read or reset operation is initiated by writing the
read/reset command sequence into the command reg-
ister. Microprocessor read cycles retrieve array data
from the memory. The device remains enabled for
reads until the command register contents are altered.
Autoselect Command
Flash memories are intended for use in applications
where the local CPU alters memory contents. As such,
manufacturer and device codes must be accessible
while the device resides in the target system. The
Am29LV008 contains an autoselect command opera-
tion that provides device information and sector protec-
tion status to the system. The operation is initiated by
writing the autoselect command sequence into the
command register. Following the command write, a
read cycle from address XX00H retrieves the manufac-
turer code of 01H. A read cycle from address XX01H
returns the device code 3EH (for top boot device) or
37H (for bottom boot device); see Table 2 on page 9.
All manufacturer and device codes will exhibit odd par-
ity with the MSB of the lower byte (DQ7) defined as the
parity bit. Scanning the sector addresses (A13, A14,
A15, A16, A17, A18, and A19) while (A6, A1, A0) = (0,
1, 0) will produce a logical ‘1’ code at device output
DQ0 for a write protected sector (See Table 2).
It is possible to determine if a sector is protected in the
system by writing an Autoselect command. Performing
a read operation at the address location XX02H, where
the higher order address A18–A12 represents the sec-
tor address, will produce a logical ‘1’ at DQ0 for a pro-
tected sector.
Temporary Sector Unprotect
The sectors of the Am29LV008 may be temporarily un-
protected by raising the RESET pin to 12.0 volts (V ).
ID
During this mode, formerly protected sectors can be
programmed or erased with standard command se-
quences by selecting the appropriate byte or sector ad-
dresses. Once the RESET pin goes to V , all the
IH
previously protected sectors will be protected again.
To terminate the Autoselect operation, it is neces-
sary to write the read/reset command sequence
into the register.
Command Definitions
Device operations are selected by writing specific ad-
dress and data sequences into the command register.
Writing incorrect address and data values or writ-
12
Am29LV008T/Am29LV008B
CYPRESS [ CYPRESS ]
