AT25DF641A datasheet(19/58 Pages) DIALOG

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AT25DF641A [DATASHEET]

8793F–DFLASH–11/2017

8.5

Program/Erase Suspend

In some code-plus-data storage applications, it is often necessary to process certain high-level system interrupts that

require relatively immediate reading of code or data from the Flash memory. In such an instance, it may not be possible

for the system to wait the microseconds or milliseconds required for the Flash memory to complete a program or erase

cycle. The Program/Erase Suspend command allows a program or erase operation in progress to a particular 64KB

sector of the Flash memory array to be suspended so that other device operations can be performed.

By suspending an erase operation to a particular sector, the system can perform a program or read operation within

another 64KB sector in the device. Other device operations, such as a Read Status Register, can also be performed

while a program or erase operation is suspended. Table 8-1 outlines the operations that are allowed and not allowed

while a program or erase operation is suspended.

Since the need to suspend a program or erase operation is immediate, the Write Enable command does not need to be

issued prior to the Program/Erase Suspend command being issued. Therefore, the Program/Erase Suspend command

operates independently of the state of the WEL bit in the Status Register.

To perform a Program/Erase Suspend, the CS pin must first be asserted and then the opcode B0h must be clocked into

the device. No address bytes need to be clocked into the device, and any data clocked in after the opcode will be

ignored. When the CS pin is deasserted, the program or erase operation currently in progress will be suspended within a

time of tSUSP. The Program Suspend (PS) bit or the Erase Suspend (ES) bit in the Status Register will then be set to the

Logical 1 state to indicate that the program or erase operation has been suspended. In addition, the RDY/BSY bit in the

Status Register will indicate that the device is ready for another operation. The complete opcode must be clocked into

the device before the CS pin is deasserted, and the CS pin must be deasserted on an even byte boundary (multiples of

eight bits); otherwise, no suspend operation will be performed.

Read operations are not allowed to a 64KB sector that has had its program or erase operation suspended. If a read is

attempted to a suspended sector, then the device will output undefined data. Therefore, when performing a Read Array

operation to an unsuspended sector, and the device’s internal address counter increments and crosses the sector

boundary to a suspended sector, the device will then start outputting undefined data continuously until the address

counter increments and crosses a sector boundary to an unsuspended sector.

A program operation is not allowed on a sector that has been erase suspended. If a program operation is attempted on

an erase suspended sector, then the program operation will abort and the WEL bit in the Status Register will be reset

back to the Logical 0 state. Likewise, an erase operation is not allowed to a sector that has been program suspended. If

attempted, the erase operation will abort and the WEL bit in the Status Register will be reset to a Logical 0 state.

During an Erase Suspend, a program operation to a different 64KB sector can be started and subsequently suspended.

This results in a simultaneous Erase Suspend/Program Suspend condition, which will be indicated by the ES and PS bits

in the Status Register being set to the Logical 1 state.

If a Reset operation (see “Reset” on page 41) is performed while a sector is erase suspended, the suspend operation will

abort and the contents of the block in the suspended sector will be left in an undefined state. However, if a Reset is

performed while a sector is program suspended, the suspend operation will abort but only the contents of the page that

was being programmed and subsequently suspended will be undefined. The remaining pages in the 64KB sector will

retain their previous contents.

If an attempt is made to perform an operation that is not allowed while a program or erase operation is suspended, such

as a Protect Sector command, then the device will simply ignore the opcode and no operation will be performed. The

state of the WEL bit in the Status Register, as well as the SPRL (Sector Protection Registers Locked) and SLE (Sector

Lockdown Enabled) bits, will not be affected.

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