AM29F002NB AMD [Advanced Micro Devices], AM29F002NB Datasheet - Page 14

• Manufacturer Part Number: AM29F002NB
• Description: 2 Megabit (256 K x 8-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

DQ7 or DQ6. See “Write Operation Status” for informa-
tion on these status bits.
Any commands written to the device during the
Embedded Program Algorithm are ignored. On the
Am29F002B only, note that a hardware reset during
the sector erase operation immediately terminates the
operation. The Sector Erase command sequence
should be reinitiated once the device has returned 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”.
Note: See the appropriate Command Definitions table for
program command sequence.
Chip Erase Command Sequence
Chip erase is a six-bus-cycle operation. The chip erase
command sequence is initiated by writing two unlock
November 28, 2000
Increment Address
Figure 2. Program Operation
in progress
Embedded
algorithm
Program
No
Command Sequence
Write Program
Last Address?
Programming
from System
Verify Data?
Completed
Data Poll
START
Yes
Yes
Am29F002B/Am29F002NB
No
cycles, followed by a set-up command. Two additional
unlock write cycles are then followed by the chip erase
command, which in turn invokes the Embedded Erase
algorithm. The device does not require the system to
preprogram prior to erase. The Embedded Erase algo-
rithm automatically preprograms and verifies the entire
memory for an all zero data pattern prior to electrical
erase. The system is not required to provide any con-
trols or timings during these operations. The Command
Definitions table shows the address and data require-
ments for the chip erase command sequence.
A ny c om ma nds wr itten to the chi p du rin g the
Embedded Erase algorithm are ignored. On the
Am29F002B only, note that a hardware reset during
the sector erase operation immediately terminates the
operation. The Sector Erase command sequence
should be reinitiated once the device has returned to
reading array data, to ensure data integrity.
The system can determine the status of the erase oper-
ation by using DQ7, DQ6, or DQ2. See “Write
Operation Status” for information on these status bits.
When the Embedded Erase algorithm is complete, the
device returns to reading array data and addresses are
no longer latched.
Figure 3 illustrates the algorithm for the erase opera-
tion. See the Erase/Program Operations tables in “AC
Characteristics” for parameters, and to the Chip/Sector
Erase Operation Timings for timing waveforms.
Sector Erase Command Sequence
Sector erase is a six bus cycle operation. The sector
erase command sequence is initiated by writing two
unlock cycles, followed by a set-up command. Two
additional unlock write cycles are then followed by the
address of the sector to be erased, and the sector
erase command. The Command Definitions table
shows the address and data requirements for the
sector erase command sequence.
The device does not require the system to preprogram
the memory prior to erase. The Embedded Erase algo-
rithm automatically programs and verifies the sector for
an all zero data pattern prior to electrical erase. The
system is not required to provide any controls or
timings during these operations.
After the command sequence is written, a sector erase
time-out of 50 µs begins. During the time-out period,
additional sector addresses and sector erase com-
mands may be written. Loading the sector erase buffer
may be done in any sequence, and the number of
sectors may be from one sector to all sectors. The time
between these additional cycles must be less than 50
µs, otherwise the last address and command might not
be accepted, and erasure may begin. It is recom-
mended that processor interrupts be disabled during
this time to ensure all commands are accepted. The
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