28F008SA datasheet(12/33 Pages) INTEL

12 / 33 page

28F008SA

Write

Writes to the Command User Interface enable read-

ing of device data and Intelligent Identifiers They

also control inspection and clearing of the Status

mand User Interface controls block erasure and byte

write The contents of the interface register serve as

input to the internal state machine

The Command User Interface itself does not occupy

an addressable memory location The interface reg-

ister is a latch used to store the command and ad-

dress and data information needed to execute the

command Erase Setup and Erase Confirm com-

mands require both appropriate command data and

an address within the block to be erased The Byte

Write Setup command requires both appropriate

command data and the address of the location to be

written while the Byte Write command consists of

the data to be written and the address of the loca-

tion to be written

The Command User Interface is written by bringing

to a logic-low level (VIL) while CE

is low

Addresses and data are latched on the rising edge

of WE

Standard microprocessor write timings are

used

Refer to AC Write Characteristics and the AC Wave-

forms for Write Operations Figure 11 for specific

timing parameters

COMMAND DEFINITIONS

When VPPL is applied to the VPP pin read opera-

tions from the Status Register intelligent identifiers

or array blocks are enabled Placing VPPH on VPP

enables successful byte write and block erase oper-

ations as well

Device operations are selected by writing specific

commands into the Command User Interface Table

3 defines the 28F008SA commands

Read Array Command

Upon initial device powerup and after exit from deep

powerdown mode the 28F008SA defaults to Read

Array mode This operation is also initiated by writing

FFH into the Command User Interface Microproces-

sor read cycles retrieve array data The device re-

mains enabled for reads until the Command User

Interface contents are altered Once the internal

Write State Machine has started a block erase or

byte write operation the device will not recognize

the Read Array command until the WSM has com-

pleted its operation The Read Array command is

functional when VPP e VPPL or VPPH

Table 4 Status Register Definitions

WSMS

ESS

BWS

VPPS

76543210

SR7 e WRITE STATE MACHINE STATUS

1 e Ready

0 e Busy

SR6 e ERASE SUSPEND STATUS

1 e Erase Suspended

0 e Erase in ProgressCompleted

SR5 e ERASE STATUS

1 e Error in Block Erasure

0 e Successful Block Erase

SR4 e BYTE WRITE STATUS

1 e Error in Byte Write

0 e Successful Byte Write

SR3 e VPP STATUS

1 e VPP Low Detect Operation Abort

0 e VPP OK

SR2–SR0 e RESERVED FOR FUTURE

ENHANCEMENTS

These bits are reserved for future use and

should be masked out when polling the Status

NOTES

RYBY

or the Write State Machine Status bit must first

be checked to determine byte write or block erase com-

pletion before the Byte Write or Erase Status bit are

checked for success

If the Byte Write AND Erase Status bits are set to ‘‘1’’s

during a block erase attempt an improper command se-

quence was entered Attempt the operation again

If VPP low status is detected the Status Register must be

cleared before another byte write or block erase opera-

tion is attempted

The VPP Status bit unlike an AD converter does not

provide continuous indication of VPP level The WSM in-

terrogates the VPP level only after the byte write or block

erase command sequences have been entered and in-

forms the system if VPP has not been switched on The

VPP Status bit is not guaranteed to report accurate feed-

back between VPPL and VPPH

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