JS28F256P33BFE datasheet(28/90 Pages) MICRON

28 / 90 page

P33-65nm

Datasheet

Aug 2009

Order Number: 320003-08

9.0

Erase Operation

Flash erasing is performed on a block basis. An entire block is erased each time an

erase command sequence is issued, and only one block is erased at a time. When a

block is erased, all bits within that block read as logical ones. The following sections

describe block erase operations in detail.

9.1

Block Erase

Block erase operations are initiated by writing the Block Erase Setup command to the

address of the block to be erased (see Section 6.2, “Device Command Bus Cycles” on

page 18). Next, the Block Erase Confirm command is written to the address of the

block to be erased. If the device is placed in standby (CE# deasserted) during an erase

operation, the device completes the erase operation before entering standby. VPP must

be above VPPLK and the block must be unlocked (see Figure 35, “Block Erase Flowchart”

on page 76).

During a block erase, the WSM executes a sequence of internally-timed events that

conditions, erases, and verifies all bits within the block. Erasing the flash memory array

changes “zeros” to “ones”. Memory array bits that are ones can be changed to zeros

only by programming the block.

The Status Register can be examined for block erase progress and errors by reading

any address. The device remains in the Read Status Register state until another

command is written. SR.0 indicates whether the addressed block is erasing. Status

Status Register bit SR.7 indicates block erase status while the sequence executes.

When the erase operation has finished, Status Register bit SR.5 indicates an erase

failure if set. SR.3 set would indicate that the WSM could not perform the erase

operation because VPP was outside of its acceptable limits. SR.1 set indicates that the

erase operation attempted to erase a locked block, causing the operation to abort.

Before issuing a new command, the Status Register contents should be examined and

then cleared using the Clear Status Register command. Any valid command can follow

once the block erase operation has completed.

9.2

Blank Check

The Blank Check operation determines whether a specified main block is blank (i.e.

completely erased). Without Blank Check, Block Erase would be the only other way to

ensure a block is completely erased. so Blank Check can be used to determine whether

or not a prior erase operation was successful; this includes erase operations that may

have been interrupted by power loss.

Blank check can apply to only one block at a time, and no operations other than Status

erase etc). Suspend and resume operations are not supported during Blank Check, nor

is Blank Check supported during any suspended operations.

Blank Check operations are initiated by writing the Blank Check Setup command to the

block address. Next, the Check Confirm command is issued along with the same block

address. When a successful command sequence is entered, the device automatically

enters the Read Status State. The WSM then reads the entire specified block, and

determines whether any bit in the block is programmed or over-erased.

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