AT49F040B ATMEL [ATMEL Corporation], AT49F040B Datasheet - Page 5

• Manufacturer Part Number: AT49F040B
• Description: 4-megabit (512K x 8) 5-volt Only Flash Memory
• Manufacturer: ATMEL [ATMEL Corporation]

4.6
4.7
4.8
4.9
4.10
3606A–FLASH–12/05
Product Identification
Data Polling
Toggle Bit
Erase/Program Status Bit
Hardware Data Protection
The product identification mode identifies the device and manufacturer as Atmel. It may be
accessed by hardware or software operation. The hardware operation mode can be used by an
external programmer to identify the correct programming algorithm for the Atmel product.
For details, see Operating Modes (for hardware operation) or Software Product Identification.
The manufacturer and device code is the same for both modes.
The AT49F040B features DATA polling to indicate the end of a program or erase cycle. During a
program cycle an attempted read of the last byte loaded will result in the complement of the
loaded data on I/O7. Once the program cycle has been completed, true data is valid on all out-
puts and the next cycle may begin. DATA polling may begin at any time during the program
cycle. During a chip or sector erase operation, an attempt to read the device will give a “0” on
I/O7. Once the erase operation is completed, a “1” will be read from I/O7. The Data Polling sta-
tus bit must be used in conjunction with the erase/program status bit as shown in the algorithm
in
In addition to DATA polling, the AT49F040B provides another method for determining the end of
a program or erase cycle. During a program or erase operation, successive attempts to read
data from the device will result in I/O6 toggling between one and zero. Once the program cycle
has completed, I/O6 will stop toggling and valid data will be read. Examining the toggle bit may
begin at any time during a program cycle. The toggle bit status bit should be used in conjunction
with the erase/program status bit shown in the algorithm in
The device offers a status bit on I/O5, which indicates whether the program or erase operation
has exceeded a specified internal pulse count limit. If the status bit is a “1”, the device is unable
to verify that an erase or a byte program operation has been successfully performed. If a pro-
gram (Sector Erase) command is issued to the boot sector and the boot sector programming
lockout feature is enabled, the boot sector will not be programmed (erased), and the device will
go into the read mode. Once the erase/program status bit has been set to a “1”, the system must
write the Product ID Exit command to return to the read mode. The erase/program status bit is a
“0” while the erase or program operation is still in progress.
Hardware features protect against inadvertent programs to the AT49F040B in the following
ways: (a) Program inhibit: holding any one of OE low, CE high or WE high inhibits program
cycles. (b) Noise filter: pulses of less than 10 ns (typical) on the WE or CE inputs will not initiate
a program cycle.
Figure 4-1 on page
6.
Figure 4-2 on page
AT49F040B
6.
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