BM29F040 Просмотр технического описания (PDF) - Winbond

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BM29F040

4 MEGABIT (512K x8) 5 VOLT SECTOR ERASE CMOS FLASH MEMORY

Winbond 

BRIGHT

Microelectronics

Inc.

Preliminary BM29F040

the four write pulse sequence. During Chip and Sector Erase, the toggle bit is valid after the rising

edge of the sixth WE pulse in the six write pulse sequence.

In programming, if the sector being written to is protected, the toggle bit may toggle for about 2 µS

and then will stop toggling without the data being changed. During erase the device will erase all the

sectors except the sector being protected. If all the sectors are protected the chip will toggle the

toggle bit for about 2 µS and then drop back to read mode without changing the data.

Either CE or OE toggling will cause the DQ6 to toggle. The toggle bit is valid in the time out period

during sector erase.

See Figure 13 for the Toggle bit timing diagrams.

DQ5 Exceeded The Timing Limits

DQ5 indicates if the program or erase time has exceeded the specified timing limits. Under these

conditions DQ5 will produce a "1". This is a failure condition which indicates that the program or erase

cycle was not successfully completed. Data polling is the only operating function of the device under

this condition. The CE circuit will partially power down the device under these conditions. The OE

and WE pins will control the output disable function as shown in Table 4.

If this failure condition occurs during the sector erase operation, it indicates that the particular sector

is bad and may not be reused. The other sectors are still functioning properly and can be used. The

device must be reset to use the other good sectors. To reset the device, write the Reset command

sequence to the device. This will allow the system to use the other active sectors in the device.

If this failure condition occurs during chip erase, it indicates that the entire chip is bad or many sectors

are bad.

If this condition occurs during byte write it indicates that the sector containing this byte is bad.

This failure condition can also occur if the user tries to program a non-blank location without erasing.

In this case the device locks out and never completes the operation. Please note that this is not a

device failure.

DQ3 Sector Erase Timer

After the completion of the Sector erase command sequence the sector erase time-out begins. DQ3

will remain low until the time-out is complete. Data polling and the Toggle bit are valid after the initial

sector erase command sequence.

If Data polling or the Toggle bit indicates the device has been written with a valid erase command,

DQ3 may be used to determine if the sector erase timer window is still open. If DQ3 is "1" the

internally controlled erase cycle has begun. If DQ3 is ″0″ the device will accept additional sector

erase commands. To ensure that the command has been accepted, the user should check the status

of DQ3 prior to and following each sector erase command. If DQ3 is "1" on the second status check,

the command may not be accepted.

Once the internal erase cycle begins the device will not accept any other command until the internal

erase cycle is completed.

The BM29F040 is designed to offer protection against accidental programming or erasure. During

power-up the device automatically resets to the read mode. The multi-bus command sequences also

provide data protection for accidental write. The device also provides additional features to prevent

inadvertent write operations during power-up and power-down transitions or system noise.

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