AM29BDD160G AMD [Advanced Micro Devices], AM29BDD160G Datasheet - Page 37

• Manufacturer Part Number: AM29BDD160G
• Description: 16 Megabit (1 M x 16-bit/512 K x 32-Bit), CMOS 2.5 Volt-only Burst Mode, Dual Boot, Simultaneous Read/Write Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

d
read/reset operating mode.
In this mode, the write protection function is by-
passed unless the PPB Lock Bit = 1.
The Accelerated Program command is not permitted
if the SecSi sector is enabled.
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram words to the device faster than using the
standard program command sequence. The unlock
bypass command sequence is initiated by first writ-
ing two unlock cycles. This is followed by a third
write cycle containing the unlock bypass command,
20h. The device 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 program command, A0h; the second
cycle contains the program address and data. Addi-
tional data is programmed in the same manner. This
mode dispenses with the initial two unlock cycles re-
quired in the standard program command sequence,
resulting in faster total programming time. Tables 18
and 20 show the requirements for the command se-
quence.
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 sys-
tem must issue the two-cycle unlock bypass reset
command sequence. The first cycle must contain the
data 90h; the second cycle the data 00h. Addresses
are don’t care for both cycles. The device then re-
turns to reading array data.
Figure 4 illustrates the algorithm for the program op-
eration. See the
AC Characteristics
for timing diagrams.
evice is in Unlock Bypass mode and during normal
Erase/Program Operations
for parameters, and to Figure 22
table in
Am29BDD160G
Note:See Tables 18 and 20 for program command
sequence.
Unlock Bypass Entry Command
The Unlock Bypass command, once issued, is used to
bypass the “unlock” sequence for program, chip
erase, and CFI commands. This feature permits slow
PROM programmers to significantly improve pro-
gramming/erase throughput since the command
sequence often requires microseconds to execute a
single write operation. Therefore, once the Unlock
Bypass command is issued, only the two-cycle pro-
gram and erase bypass commands are required. The
Unlock Bypass Command is ignored if the SecSi sec-
tor is enabled. To return back to normal operation,
the Unlock Bypass Reset Command must be issued.
The following four sections describe the commands
that may be executed within the unlock bypass
mode.
Unlock Bypass Program Command
The Unlock Bypass Program command is a two-cycle
command that consists of the actual program com-
m a n d ( A 0 h ) a n d t h e p r o g r a m a d d r e s s / d a t a
combination. This command does not require the
two-cycle “unlock” sequence since the Unlock Bypass
command was previously issued. As with the stan-
dard program command, multiple Unlock Bypass
Program commands can be issued once the Unlock
Bypass command is issued.
To return back to standard read operations, the Un-
lock Bypass Reset command must be issued.
The Unlock Bypass Program Command is ignored if
the SecSi sector is enabled.
Figure 4. Program Operation
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