5

3606A–FLASH–12/05

AT49F040B

4.6

Product Identification

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.

4.7

Data Polling

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 Figure 4-1 on page 6.

4.8

Toggle Bit

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 Figure 4-2 on page 6.

4.9

Erase/Program Status Bit

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.

4.10

Hardware Data Protection

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.