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3626A–FLASH–2/07

AT49BV802D(T)

4.6.3

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/word program operation has been successfully performed. If a

program (Sector Erase) command is issued to a protected sector, the protected sector will not

be programmed (erased). The device will go to a status read mode and the I/O5 status bit will be

set high, indicating the program (erase) operation did not complete as requested. Once the

erase/program status bit has been set to a “1”, the system must write the Product ID Exit com-

mand to return to the read mode. The erase/program status bit is a “0” while the erase or

program operation is still in progress. Please see “Status Bit Table” on page 12 for more details.

4.7

Sector Lockdown

Each sector has a programming lockdown feature. This feature prevents programming of data in

the designated sectors once the feature has been enabled. These sectors can contain secure

code that is used to bring up the system. Enabling the lockdown feature will allow the boot code

to stay in the device while data in the rest of the device is updated. This feature does not have to

be activated; any sector’s usage as a write-protected region is optional to the user.

At power-up or reset, all sectors are unlocked. To activate the lockdown for a specific sector, the

six-bus cycle Sector Lockdown command must be issued. Once a sector has been locked down,

the contents of the sector is read-only and cannot be erased or programmed.

4.7.1

Sector Lockdown Detection

A software method is available to determine if programming of a sector is locked down. When

if programming the sector is locked down. If the data on I/O0 is low, the sector can be pro-

grammed; if the data on I/O0 is high, the program lockdown feature has been enabled and the

sector cannot be programmed. The software product identification exit code should be used to

return to standard operation.

4.7.2

Sector Lockdown Override

The only way to unlock a sector that is locked down is through reset or power-up cycles. After

power-up or reset, the content of a sector that is locked down can be erased and reprogrammed.

4.8

Erase Suspend/Erase Resume

The Erase Suspend command allows the system to interrupt a sector or chip erase operation

and then program or read data from a different sector within the memory. After the Erase Sus-

pend command is given, the device requires a maximum time of 15 µs to suspend the erase

operation. After the erase operation has been suspended, the system can then read data or pro-

gram data to any other sector within the device. An address is not required during the Erase

Suspend command. During a sector erase suspend, another sector cannot be erased. To

resume the sector erase operation, the system must write the Erase Resume command. The

Erase Resume command is a one-bus cycle command. The device also supports an erase sus-

pend during a complete chip erase. While the chip erase is suspended, the user can read from

any sector within the memory that is protected. The command sequence for a chip erase sus-

pend and a sector erase suspend are the same.