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NX26F011A Datasheet(PDF) 4 Page - List of Unclassifed Manufacturers

Part No. NX26F011A
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NexFlash Technologies, Inc.
05/05/99 ©
The instruction sequence format, flow charts, and clocking
diagrams for Read and Erase/Write operations are shown in
Figures 5 and 6, Figures 7 and 8, and Figures 9 and 10,
respectively. All data within an instruction sequence is
clocked on the rising edge. All instruction sequence fields are
ordered by most significant bit first (MSB). Data is erased and
written to the NX26F041A and NX26F011A memory array a
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.
To ensure the highest level of data integrity write operations
should be verified and rewritten, if needed, (see High Data
Integrity Applications).
Reset and Idle
Upon power-up and between Read and Erase/Write instruc-
tion sequences, the device’s internal control logic will be
reset. This is accomplished by asserting the SCK pin low
(to VIL) for greater than
tRESET (~5 ms to 10 ms depending on
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.
Device Initialization
After power-up it is recommended that the device information
sector be read to electronically identify the device. The
device information format contains a device ID that identifies
the manufacturer, part number (memory size), and operating
range. It also contains a list of any restricted sectors
(see Sector Tag/Sync bytes). For a further description of the
NX26F011A and NX26F041A device information format, see
the Serial Flash Device Information Sector Application Note
As shown in Figure 6, the address for the device information
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.
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
will not exceed tWP (~5 to 30 ms based on the specified power
supply operating voltage). During this time the device can be
tested for a Ready/Busy condition via a 16-bit status value
obtained in the Read instruction sequence. The Busy status
condition (6666H) indicates that the device has not yet
completed its write operation and will not accept read or write
instructions. The Ready status condition (9999H) indicates
that the device is available for further read or write operations.
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.
Sector Tag/Sync Bytes
The first byte of each sector is pre-programmed during
manufacturing with a Tag/Sync value of “C9H”. Although the
first byte of each sector can be changed, it is recommended
that Tag/Sync value be maintained and incorporated as part
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
the device properly. Secondly, they serve as a tag to identify
a fully functional (valid) sector. This is especially important
if “restricted sector” devices are used.
Restricted sector devices provide a more cost effective
alternative to NX26F011A or NX26F041A devices with 100%
valid sectors. Restricted sector devices have a limited
number of sectors (32 maximum. for the NX26F011A and
NX26F041A) that do not meet manufacturing programming
criteria over the specified operating range. When such a
sector is detected, the first byte is tagged with a pattern other
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).
High Data Integrity Applications
Data storage applications that use Flash memory or other
non-volatile media must take into consideration the possibil-
ity of noise or other adverse system conditions that may
affect data integrity. For those applications that require higher
levels of data integrity it is a recommended practice to use
Error Correcting Code (ECC) techniques. The NexFlash
Serial Flash Development Kit provides a software routine for
a 32-bit ECC that can detect up to two bit errors and correct
one. The ECC not only minimizes problems caused by
system noise but can also extend Flash memory endurance.
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
compare data written to a given sector and rewrite the sector
if the compare is not correct.

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