UPSD3422 datasheet(205/293 Pages) STMICROELECTRONICS

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uPSD34xx

PSD module

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28.5.7

Toggle flag (DQ6)

The Flash memories offer an alternate way to determine when a Flash memory program

operation has completed. During the program operation and while the correct sector select

FSx or CSBOOTx is active, the Toggle Flag Bit (DQ6) toggles from '0' to '1' and '1' to ’0’ on

subsequent attempts to read any byte of the same Flash array.

When the internal program operation is complete, the toggling stops and the data read on

the data bus D0-7 is the actual value of the addressed memory byte. The device is now

accessible for a new READ or WRITE operation. The operation is finished when two

successive READs yield the same value for DQ6.

DQ6 may also be used to indicate when an erase operation has completed. During an erase

operation, DQ6 will toggle from '0' to '1' and '1' to ’0’ until the erase operation is complete,

then DQ6 stops toggling. The erase is finished when two successive READs yield the same

value of DQ6. The correct sector select signal, FSx or CSBOOTx, must be active during the

entire procedure.

DQ6 is valid after the fourth instruction byte WRITE operation (for program instruction

sequence) or after the sixth instruction byte WRITE operation (for erase instruction

sequence).

If all the Flash memory sectors selected for erasure are protected, DQ6 toggles to ’0’ for

about 100µs, then returns value of D6 of the previously addressed byte.

Error Flag (DQ5). During a normal program or erase operation, the Error Flag Bit (DQ5) is

to ’0’. This bit is set to ’1’ when there is a failure during Flash memory byte program, sector

erase, or bulk erase operations.

In the case of Flash memory programming, DQ5 Bit indicates an attempt to program a Flash

memory bit from the programmed state of '0,' to the erased state of 1, which is not valid.

DQ5 may also indicate a particular Flash cell is damaged and cannot be programmed.

In case of an error in a Flash memory sector erase or byte program operation, the Flash

memory sector in which the error occurred or to which the programmed byte belongs must

no longer be used. Other Flash memory sectors may still be used. DQ5 is reset after a

Reset Flash instruction sequence.

28.5.8

Erase time-out flag (DQ3)

The Erase Time-out Flag Bit (DQ3) reflects the time-out period allowed between two

consecutive sector erase instruction sequence bytes. If multiple sector erase commands are

desired, the additional sector erase commands (30h) must be sent by the 8032 within 80us

after the previous sector erase command. DQ3 is 0 before this time period has expired,

indicating it is OK to issue additional sector erase commands. DQ3 will go to logic ’1’ if the

time has been longer than 80µs since the previous sector erase command (time has

expired), indication that is not OK to send another sector erase command. In this case, the

8032 must start a new sector erase instruction sequence (unlock and command) beginning

again after the current sector erase operation has completed.

28.5.9

Programming Flash memory.

When a byte of Flash memory is programmed, individual bits are programmed to logic '0.'

cannot program a bit in Flash memory to a logic ’1’ once it has been programmed to a logic

'0.' A bit must be erased to logic ’1’, and programmed to logic '0.' That means Flash memory

must be erased prior to being programmed. A byte of Flash memory is erased to all 1s

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