FLASH

AS29F040

Micross Components reserves the right to change products or specifications without notice.

8

AS29F040

Rev. 2.3 01/10

Sector Erase Command Sequence

Sector erase is a six bus cycle operation. The sector erase

command sequence is initiated by writing two unlock cycles,

followed by a set-up command. Two additional unlock write

cycles are then followed by the addresss of the sector to be

erased, and the sector erase command. The Command

Defi-

nitions table shows the address and data requirements for the

sector erase command sequence.

The device does not require the system to preprogram

the memory prior to erase. The Embedded Erase algorithm

automatically programs and verifies the sector for an all zero

data pattern prior to electrical erase. The system is not required

to provide any controls or timings during these operations.

After the command sequence is written, a sector erase

time-out of 50μs begins. During the time-out period, additional

sector addresses and sector erase commands may be written.

Loading the sector erase buffer may be done in any sequence,

and the number of sectors may be from one sector to all sec-

tors. The time between these additional cycles must be less

than 50μs, otherwise the last address and command might not

be accepted, and erasure may begin. It is recommended that

processor interrupts be disabled during this time to ensure all

commands are accepted. The interrupts can be re-enabled after

the last Sector Erase command is written. If the time between

additional sector erase commands can be assumed to be less

than 50μs, the system need not monitor DQ3. Any command

other than Sector Erase or Erase Suspend during the time-out

period resets the device to reading array data. The system

must rewrite the command sequence and any additional sector

addresses and commands.

The system can monitor DQ3 to determine if the sector

erase timer has timed out. (See the “DQ3: Sector Erase Timer”

section.) The time-out begins from the rising edge of the final

WE\ pulse in the command sequence.

Once the sector erase operation has begun, only the

Erase Suspend command is valid. All other commands are

ignored.

When the Embedded Erase algorithm is complete, the

device returns to reading array data and addresses are no

longer latched. The system can determine the status of the

erase operation by using DQ7, DQ6, or DQ2. Refer to “Write

Operation Status” for information on these status bits.

Figure 2 illustrates the algorithm for the erase operation.

Refer to the Erase/Program Operations tables in the “AC

Characteristics” section for parameters, and to the Sector Erase

Operations Timing diagram for timing waveforms.

Erase Suspend/Erase Resume Commands

The Erase Suspect command allows the system to

inter-

rupt a sector erase operation and then read data from, or program

data to, any sector not selected for erasure. This command

NOTE:

1) See the appropriate Command Definitions table for program command

sequence.

2) See “DQ3: Sector Erase Timer” for more information.

FIGURE 2: ERASE OPERATION

is valid only during the sector erase operation,

including

the 50μs time-out period during the sector erase command

sequence. The Erase Suspend command is ignored if written

during the chip erase operation or Embedded Program algo-

rithm. Writing the Erase Suspect command during the Sector

Erase time-out immediately terminates the time-out

period

and suspends the erase operation. Addresses are “don’t cares”

when writing the Erase Suspect command.

When the Erase Suspect command is written during

a sector erase operation, the device requires a maximum of

20μs to suspend the erase operation. However, when the Erase

Suspend command is written during the sector erase time-out,

the device immediately terminates the time-out period and

suspends the erase operation.

After the erase operation has been suspected, the system

can read array data from any sector not selected for erasure.

(The device “erase suspends” all sectors selected for erasure.)

Normal read and write timings and command definitions ap-

ply. Reading at any address within erase-suspended sectors

produces status data on DQ7-DQ0. The system can use DQ7,

or DQ6 and DQ2 together, to determine if a sector is actively

erasing or is erase-suspended. See “Write Operation Status”

for information on these status bits.