am42bds640ag Meet Spansion Inc., am42bds640ag Datasheet - Page 29

• Manufacturer Part Number: am42bds640ag
• Description: 64 Megabit 4 M ? 16-bit Cmos 1.8 Volt-only, Simultaneous Operation, Burst Mode Flash Memory And 16 Mbit 1 M ? 16-bit Static Ram Preliminary
• Manufacturer: Meet Spansion Inc.

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
cycles in length instead of six cycles. See
details on the unlock bypass command sequences.
Figure 2 illustrates the algorithm for the erase opera-
tion. Refer to the Erase/Program Operations table in
the AC Characteristics section for parameters and
timing diagrams.
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 cycles are written, and are then fol-
lowed by the address of the sector to be erased, and
the sector erase command.
address and data requirements for the sector erase
command sequence.
The device does not require the system to preprogram
prior to erase. The Embedded Erase algorithm auto-
matically 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 sec-
tors. The time between these additional cycles must be
less than 50 µs, otherwise erasure may begin. Any
sector erase address and command following the
exceeded time-out may or may not be accepted. It is
recommended that processor interrupts 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 sequence and any addi-
tional addresses and commands.
The system can monitor DQ3 to determine if the sector
erase timer has timed out (See
Timer” section on page
the rising edge of the final WE# pulse in the command
sequence.
28
34.). The time-out begins from
Table 14
“DQ3: Sector Erase
Table 14
shows the
P R E L I M I N A R Y
Am42BDS640AG
for
When the Embedded Erase algorithm is complete, the
bank returns to reading array data and addresses are
no longer latched. Note that while the Embedded Erase
operation is in progress, the system can read data from
the non-erasing bank. The system can determine the
status of the erase operation by reading DQ7 or
DQ6/DQ2 in the erasing bank. Refer to the
Operation Status” section on page 31
mation on these status bits.
Once the sector erase operation has begun, only the
Erase Suspend command is valid. All other commands
are ignored. However, note that a hardware reset
immediately terminates the erase operation. If that
occurs, the sector 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 sector erase
command sequence while the device is in the unlock
bypass mode. The command sequence is four cycles
cycles in length instead of six cycles.
Figure 2
tion. Refer to the Erase/Program Operations table in
the AC Characteristics section for parameters and
timing diagrams.
Erase Suspend/Erase Resume Commands
The Erase Suspend command, B0h, allows the system
to interrupt a sector erase operation and then read data
from, or program data to, any sector not selected for
erasure. The bank address is required when writing
this command. This command is valid only during the
sector erase operation, including the minimum 50 µs
time-out period during the sector erase command
sequence. The Erase Suspend command is ignored if
written during the chip erase operation or Embedded
Program algorithm.
When the Erase Suspend command is written during
the sector erase operation, the device requires a
maximum of 35 µs to suspend the erase operation.
However, when the Erase Suspend command is
written during the sector erase time-out, the device
immediately terminates the time-out period and sus-
pends the erase operation.
After the erase operation has been suspended, the
bank enters the erase-suspend-read mode. The
system can read data from or program data to any
sector not selected for erasure. (The device “erase
suspends” all sectors selected for erasure.) Reading at
any address within erase-suspended sectors produces
status information on DQ7–DQ0. The system can use
DQ7, or DQ6 and DQ2 together, to determine if a
sector is actively erasing or is erase-suspended. Refer
to the Write Operation Status section for information on
these status bits.
illustrates the algorithm for the erase opera-
November 1, 2002
section for infor-
“Flash Write