A D V A N C E I N F O R M A T I O N
the same manner. This mode dispenses with the initial
and CFI commands. This feature permits slow PROM
programmers to significantly improve program-
ming/erase throughput since the command sequence
often requires microseconds to execute a single write
operation. Therefore, once the Unlock Bypass com-
mand is issued, only the two-cycle program and erase
bypass commands are required. The Unlock Bypass
Command is ignored if the SecSi sector is enabled. To
return back to normal operation, the Unlock Bypass
Reset Command must be issued.
two unlock cycles required in the standard program
command sequence, resulting in faster total program-
ming time. Tables 18 and 20 show the requirements 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. 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 returns to
reading array data.
The following four sections describe the commands
that may be executed within the unlock bypass mode.
Unlock Bypass Program Command
Figure 5 illustrates the algorithm for the program oper-
ation. See the Erase/Program Operations table in AC
Characteristics for parameters, and to Figure 22 for
timing diagrams.
The Unlock Bypass Program command is a two-cycle
command that consists of the actual program com-
mand (A0h) and the program address/data combina-
tion. This command does not require the two-cycle
“unlock” sequence since the Unlock Bypass command
was previously issued. As with the standard program
command, multiple Unlock Bypass Program com-
mands can be issued once the Unlock Bypass com-
mand is issued.
START
To return back to standard read operations, the Unlock
Bypass Reset command must be issued.
Write Program
Command Sequence
The Unlock Bypass Program Command is ignored if
the SecSi sector is enabled.
Data Poll
from System
Unlock Bypass Chip Erase Command
Embedded
Program
algorithm
in progress
The Unlock Bypass Chip Erase command is a 2-cycle
command that consists of the erase setup command
(80h) and the actual chip erase command (10h). This
command does not require the two-cycle “unlock” se-
quence since the Unlock Bypass command was previ-
ously issued. Unlike the standard erase command,
there is no Unlock Bypass Erase Suspend or Erase
Resume commands.
Verify Data?
No
Yes
No
To return back to standard read operations, the Unlock
Bypass Reset command must be issued.
Increment Address
Last Address?
Yes
The Unlock Bypass Program Command is ignored if
the SecSi sector is enabled.
Programming
Completed
Unlock Bypass CFI Command
The Unlock Bypass CFI command is available for
PROM programmers and target systems to read the
CFI codes while in Unlock Bypass mode. See Com-
mon Flash Memory Interface (CFI) for specific CFI
codes.
Note: See Tables 18 and 20 for program command se-
quence.
Figure 4. Program Operation
To return back to standard read operations, the Unlock
Bypass Reset command must be issued.
Unlock Bypass Entry Command
The Unlock Bypass Program Command is ignored if
the SecSi sector is enabled.
The Unlock Bypass command, once issued, is used to
bypass the “unlock” sequence for program, chip erase,
April 8, 2003
Am29BDD160G
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