AM29BDS640G SPANSION [SPANSION], AM29BDS640G Datasheet - Page 36

• Manufacturer Part Number: AM29BDS640G
• Description: 64 Megabit (4 M x 16-Bit) CMOS 1.8 Volt-only Simultaneous Read/Write, Burst Mode Flash Memory
• Manufacturer: SPANSION [SPANSION]

34
Chip Erase Command Sequence
Sector Erase Command Sequence
Chip erase is a six bus cycle operation. The chip erase command sequence is ini-
tiated by writing two unlock 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 algorithm auto-
matically preprograms and verifies the entire memory for an all zero data pattern
prior to electrical erase. The system is not required to provide any controls or tim-
ings during these operations.
shows the address and data requirements for the chip erase command sequence.
When the Embedded Erase algorithm is complete, that bank returns to the read
mode and addresses are no longer latched. The system can determine the status
of the erase operation by using DQ7 or DQ6/DQ2. Refer to the “Write Operation
Status” section for information on these status bits.
Any commands written during the chip erase operation are ignored. However,
note that a hardware reset immediately terminates the erase operation. If that
occurs, the chip erase command sequence should be reinitiated once that bank
has returned to reading array data, to ensure data integrity.
The host system may also initiate the chip erase command sequence while the
device is in the unlock bypass mode. The command sequence is two cycles in
length instead of six cycles. See
mand sequences.
Figure 2
gram Operations table in the AC Characteristics section for parameters and timing
diagrams.
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 addi-
tional unlock cycles are written, and are then followed by the address of the
sector to be erased, and the sector erase command.
and data requirements for the sector erase command sequence.
The device does not require the system to preprogram prior to erase. The Em-
bedded Erase algorithm automatically programs and verifies the entire memory
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 no less than
35 µs occurs. During the time-out period, additional sector addresses and sector
erase commands 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 era-
sure may begin. Any sector erase address and command following the exceeded
time-out may or may not be accepted. It is recommended that processor inter-
rupts be disabled during this time to ensure all commands are accepted. The
interrupts can be re-enabled after the last Sector Erase command is written. Any
command other than Sector Erase or Erase Suspend during the time-out period
resets that bank to the read mode. The system must rewrite the command se-
quence and any additional addresses and commands.
illustrates the algorithm for the erase operation. Refer to the Erase/Pro-
Table 13, “Command Definitions,” on page 37
Table 13
Am29BDS640G
P r e l i m i n a r y
for details on the unlock bypass com-
Table 13
shows the address
25903C1 October 1, 2003