AM29DL640D120 AMD [Advanced Micro Devices], AM29DL640D120 Datasheet - Page 25

• Manufacturer Part Number: AM29DL640D120
• Description: 64 Megabit CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

Sector command sequence. The device continues to
access the SecSi Sector region until the system is-
sues the four-cycle Exit SecSi Sector command
sequence. The Exit SecSi Sector command sequence
returns the device to normal operation. The SecSi
Sector is not accessible when the device is executing
an Embedded Program or embedded Erase algorithm.
Table 12 shows the address and data requirements for
both command sequences. See also “SecSi™ (Se-
cured Silicon) Sector Flash Memory Region” for further
information. Note that the ACC function and unlock by-
pass modes are not available when the SecSi Sector
is enabled.
Byte/Word Program Command Sequence
The system may program the device by word or byte,
depending on the state of the BYTE# pin. Program-
ming is a four-bus-cycle operation. The program
command sequence is initiated by writing two unlock
write cycles, followed by the program set-up com-
mand. The program address and data are written next,
which in turn initiate the Embedded Program algo-
rithm. The system is not required to provide further
controls or timings. The device automatically provides
internally generated program pulses and verifies the
programmed cell margin. Table 12 shows the address
and data requirements for the byte program command
sequence. Note that the SecSi Sector, autoselect, and
CFI functions are unavailable when a program opera-
tion in is progress.
When the Embedded Program algorithm is complete,
that bank then returns to the read mode and ad-
dresses are no longer latched. The system can
determine the status of the program operation by
using DQ7, DQ6, or RY/BY#. Refer to the Write Oper-
ation Status section 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
operation. The program command sequence should
be reinitiated once that bank has returned to the read
mode, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from “0” back to a “1.” Attempting to do so may
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Am29DL640D
cause that bank to set DQ5 = 1, or cause the DQ7 and
DQ6 status bits to indicate the operation was success-
ful. However, a succeeding read will show that the
data is still “0.” Only erase operations can convert a “0”
to a “1.”
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram bytes or words to a bank faster than using the
standard program command sequence. The unlock
bypass command sequence is initiated by first writing
two unlock cycles. This is followed by a third write
cycle containing the unlock bypass command, 20h.
That bank then enters the unlock bypass mode. A
two-cycle unlock bypass program command sequence
is all that is required to program in this mode. The first
cycle in this sequence contains the unlock bypass pro-
gram command, A0h; the second cycle contains the
program address and data. Additional data is pro-
grammed in the same manner. This mode dispenses
with the initial two unlock cycles required in the stan-
dard program command sequence, resulting in faster
total programming time. Table 12 shows the require-
ments for the command sequence.
During the unlock bypass mode, only the Unlock By-
pass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
must issue the two-cycle unlock bypass reset com-
mand sequence. (See Table 12).
The device offers accelerated program operations
through the WP#/ACC pin. When the system asserts
V
ters the Unlock Bypass mode. The system may then
write the two-cycle Unlock Bypass program command
sequence. The device uses the higher voltage on the
WP#/ACC pin to accelerate the operation. Note that
the WP#/ACC pin must not be at V
other than accelerated programming, or device dam-
age may result. In addition, the WP#/ACC pin must not
be left floating or unconnected; inconsistent behavior
of the device may result.
Figure 4 illustrates the algorithm for the program oper-
ation. Refer to the Erase and Program Operations
table in the AC Characteristics section for parameters,
and Figure 18 for timing diagrams.
HH
on the WP#/ACC pin, the device automatically en-
HH
October 7, 2004
any operation