NX26F011A
NX26F041A
supplyoperatingvoltage).Duringthistimethedevicecanbe
tested for a Ready/Busy condition via a 16-bit status value
obtainedintheReadinstructionsequence.TheBusystatus
condition (6666H) indicates that the device has not yet
completeditswriteoperationandwillnotacceptreadorwrite
instructions. The Ready status condition (9999H) indicates
thatthedeviceisavailableforfurtherreadorwriteoperations.
Note that a delay time of tRP (~30 µs to 100 µs depending on
the voltage version being used) is required after the first low
to high clock transition of the Ready/Busy status read.
The instruction sequence format, flow charts, and clocking
diagramsforReadandErase/Writeoperationsareshownin
Figures 5 and 6, Figures 7 and 8, and Figures 9 and 10,
respectively. All data within an instruction sequence is
clockedontherisingedge.Allinstructionsequencefieldsare
orderedbymostsignificantbitfirst(MSB).Dataiserasedand
writtentotheNX26F041AandNX26F011Amemoryarraya
full sector (264 bytes) at a time. If all 264 bytes of a given
sector are not fully clocked into the device, the remaining
byte locations will be overwritten with indeterminate values.
Toensurethehighestlevelofdataintegritywriteoperations
should be verified and rewritten, if needed, (see High Data
Integrity Applications).
SectorTag/SyncBytes
The first byte of each sector is pre-programmed during
manufacturingwithaTag/Syncvalueof“C9H”.Althoughthe
first byte of each sector can be changed, it is recommended
thatTag/Syncvaluebemaintainedandincorporatedaspart
of the application’s sector formatting. The Tag/Sync values
serve two purposes. First, they provide a sync-detect that
can help verify if the instruction sequence was clocked into
thedeviceproperly.Secondly,theyserveasatagtoidentify
a fully functional (valid) sector. This is especially important
if “restricted sector” devices are used.
Reset and Idle
Uponpower-upandbetweenReadandErase/Writeinstruc-
tion sequences, the device’s internal control logic will be
reset. This is accomplished by asserting the SCK pin low
(toVIL)forgreaterthantRESET (~5msto10msdependingon
the voltage version being used). Once reset, the device
enters standby operation and will not wake-up until the next
rising edge of SCK. After an initial rising SCK occurs, the
device becomes ready for a new instruction sequence. Full
active power consumption starts after the correct device
address is decoded during a Read or Write instruction
sequence. To idle an instruction sequence between clocks,
SCK must be kept high (at VIH) for as long as needed. Note
that power will be in the active state when SCK is held high.
Restricted sector devices provide a more cost effective
alternativetoNX26F011AorNX26F041Adeviceswith100%
valid sectors. Restricted sector devices have a limited
number of sectors (32 maximum. for the NX26F011A and
NX26F041A)thatdonotmeetmanufacturingprogramming
criteria over the specified operating range. When such a
sectorisdetected,thefirstbyteistaggedwithapatternother
than “C9H”. In addition to individual sector tagging, all
restricted sectors for a given device are listed in the “device
information format” (see Device Initialization).
DeviceInitialization
Afterpower-upitisrecommendedthatthedeviceinformation
sector be read to electronically identify the device. The
deviceinformationformatcontainsadeviceIDthatidentifies
themanufacturer,partnumber(memorysize),andoperating
range. It also contains a list of any restricted sectors
(seeSectorTag/Syncbytes).Forafurtherdescriptionofthe
NX26F011AandNX26F041Adeviceinformationformat,see
theSerialFlashDeviceInformationSectorApplicationNote
SFAN-02.
HighDataIntegrityApplications
Data storage applications that use Flash memory or other
non-volatilemediamusttakeintoconsiderationthepossibil-
ity of noise or other adverse system conditions that may
affectdataintegrity.Forthoseapplicationsthatrequirehigher
levels of data integrity it is a recommended practice to use
Error Correcting Code (ECC) techniques. The NexFlash
SerialFlashDevelopmentKitprovidesasoftwareroutinefor
a 32-bit ECC that can detect up to two bit errors and correct
one. The ECC not only minimizes problems caused by
systemnoisebutcanalsoextendFlashmemoryendurance.
For those systems without the processing power to handle
ECC algorithms, a simple “verification after write” is recom-
mended. The NexFlash Serial Flash Development Kit
software includes a simple Write/Verify routine that will
comparedatawrittentoagivensectorandrewritethesector
if the compare is not correct.
AsshowninFigure6, theaddressforthedeviceinformation
sector address is at 5000H for both the NX26F011A and
NX26F041A. The device information sector is a “read-only”
sector. This assures that all device specific information,
such as the restricted sector list, is maintained and never
written over inadvertently.
Ready/BusyStatus
After an Erase/Write instruction sequence has been
executed, the device will become Busy while it erases and
writes the addressed sector’s memory. This period of time
willnotexceedtWP (~5to30msbasedonthespecifiedpower
4
NexFlashTechnologies, Inc.
PRELIMINARYNXSF009A-0599
05/05/99 ©