AM29LV002 Datasheet, PDF (12/34 Pages) Advanced Micro Devices – 2 Megabit (256 K x 8-Bit) CMOS 3.0 Volt-only, Boot Sector Flash Memory

PRELIMINARY
Autoselect Command Sequence
The autoselect command sequence allows the host
system to access the manufacturer and devices codes,
and determine whether or not a sector is protected.
Table 5 shows the address and data requirements.
This method is an alternative to that shown in Table 4,
which is intended for PROM programmers and requires
V_ID on address bit A9.
The autoselect command sequence is initiated by writ-
ing two unlock cycles, followed by the autoselect com-
mand. The device then enters the autoselect mode,
and the system may read at any address any number
of times, without initiating another command sequence.
A read cycle at address XX00h retrieves the manufac-
turer code. A read cycle at address XX01h returns the
device code. A read cycle containing a sector address
(SA) and the address 02h returns 01h if that sector is
protected, or 00h if it is unprotected. Refer to Tables 2
and 3 for valid sector addresses.
The system must write the reset command to exit the
autoselect mode and return to reading array data.
Byte Program Command Sequence
Programming is a four-bus-cycle operation. The pro-
gram command sequence is initiated by writing two un-
lock write cycles, followed by the program set-up
command. The program address and data are written
next, which in turn initiate the Embedded Program al-
gorithm. The system is not required to provide further
controls or timings. The device automatically provides
internally generated program pulses and verify the pro-
grammed cell margin. Table 5 shows the address and
data requirements for the byte program command se-
quence.
When the Embedded Program algorithm is complete,
the device then returns to reading array data and ad-
dresses are no longer latched. The system can deter-
mine the status of the program operation by using
DQ7, DQ6, or RY/BY#. See “Write Operation Status”
for information on these status bits.
Any commands written to the device during the Em-
bedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program-
ming operation. The Byte Program command se-
quence should be reinitiated once the device has reset
to reading array data, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from a “0” back to a “1”. Attempting to do so may halt
the operation and set DQ5 to “1,” or cause the Data#
Polling algorithm to indicate the operation was suc-
cessful. However, a succeeding read will show that the
data is still “0”. Only erase operations can convert a “0”
to a “1”.
Figure 2 illustrates the algorithm for the program oper-
ation. See the Erase and Program Operations table in
“AC Characteristics” for parameters, and to Figure 14
for timing diagrams
START
Write Program
Command Sequence
Embedded
Program
algorithm
in progress
Data Poll
from System
Verify Data?
No
Yes
Increment Address
No
Last Address?
Yes
Programming
Completed
Note: See Table 5 for program command sequence.
Figure 2. Program Operation
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Am29LV002