256Mb, 512Mb, 1Gb, 2Gb: 3V Embedded Parallel NOR Flash
Bypass Operations
Bypass Operations
UNLOCK BYPASS Command
The UNLOCK BYPASS (20h) command is used to place the device in unlock bypass
mode. Three bus WRITE operations are required to issue the UNLOCK BYPASS com-
mand.
When the device enters unlock bypass mode, the two initial UNLOCK cycles required
for a standard PROGRAM or ERASE operation are not needed, thus enabling faster total
program or erase time.
The UNLOCK BYPASS command is used in conjunction with UNLOCK BYPASS PRO-
GRAM or UNLOCK BYPASS ERASE commands to program or erase the device faster
than with standard PROGRAM or ERASE commands. When the cycle time to the device
is long, considerable time savings can be gained by using these commands. When in
unlock bypass mode, only the following commands are valid:
• The UNLOCK BYPASS PROGRAM command can be issued to program addresses
within the device.
• The UNLOCK BYPASS BLOCK ERASE command can then be issued to erase one or
more memory blocks.
• The UNLOCK BYPASS CHIP ERASE command can be issued to erase the whole mem-
ory array.
• The UNLOCK BYPASS WRITE TO BUFFER PROGRAM command can be issued to
speed up the programming operation.
• The UNLOCK BYPASS RESET command can be issued to return the device to read
mode.
In unlock bypass mode, the device can be read as if in read mode.
In addition to the UNLOCK BYPASS command, when VPP/WP# is raised to VPPH, the de-
vice automatically enters unlock bypass mode. When VPP/WP# returns to VIH or VIL, the
device is no longer in unlock bypass mode and normal operation resumes. The transi-
tions from VIH to VPPH and from VPPH to VIH must be slower than tVHVPP (see the Accel-
erated Program, Data Polling/Toggle AC Characteristics).
Note: Micron recommends the user enter and exit unlock bypass mode using ENTER
UNLOCK BYPASS and UNLOCK BYPASS RESET commands rather than raising VPP/WP#
to VPPH. VPP/WP# should never be raised to VPPH from any mode except read mode; oth-
erwise, the device may be left in an indeterminate state.
UNLOCK BYPASS RESET Command
The UNLOCK BYPASS RESET (90/00h) command is used to return to read/reset mode
from unlock bypass mode. Two bus WRITE operations are required to issue the UN-
LOCK BYPASS RESET command. The READ/RESET command does not exit from un-
lock bypass mode.
PDF: 09005aef849b4b09
m29ew_256mb_2gb.pdf - Rev. B 8/12 EN
Micron Technology, Inc. reserves the right to change products or specifications without notice.
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