1M / 2M / 4M-BIT SERIAL FLASH MEMORY with 40MHz SPI
NX25P10,NX25P20ANDNX25P40
SPI OPERATION
WriteProtectFeatures
SPI Modes
The NX25P10/20/40 is accessed through an SPI compat-
iblebusconsistingoffoursignals:SerialClock(CLK),Chip
Select (CS), Serial Data Input (DI) and Serial Data Output
(DO).BothSPIbusoperationModes0(0,0)and3(1,1)are
supported. The primary difference between Mode 0 and
Mode 3 concerns the normal state of the CLK signal when
the SPI bus master is in standby and data is not being
transferred to the Serial Flash. For Mode 0 the CLK signal
isnormallylow.ForMode3theCLKsignalisnormallyhigh.
In either case data input on the DI pin is sampled on the
risingedgeoftheCLK.DataoutputontheDOpinisclocked
out on the falling edge of CLK.
1
• Device resets when Vcc is below threshold.
• Time delay write disable after Power-up.
• Writeenable/disableinstructions.
2
• Automatic write disable after program and erase.
• Software write protection using Status Register.
• Hardware write protection using Status Register and
WP pin.
3
• WriteProtectionusingPower-downinstruction.
4
Upon power-up or at power-down the NX25P10/20/40 will
maintain a reset condition while Vcc is below the threshold
value of VWI, (See Power-up Timing and Voltage Levels:
Table 7 and Figure 17). While reset, all operations are
disabledandnoinstructionsarerecognized.Duringpower-
up and after the Vcc voltage exceeds VWI, all program and
erase related instructions are further disabled for a time
delay of tPUW. This includes the Write Enable, Page Pro-
gram, Sector Erase, Bulk Erase and the Write Status
Register instructions. Note that the chip select pin (CS)
must track the Vcc supply level at power-up until the Vcc-
minlevelandtVSL timedelayisreached.Ifneededapull-up
resister on CS can be used to accomplish this.
HoldFunction
TheHOLDsignalallowstheNX25P10/20/40operationtobe
paused while it is actively selected (when CS is low). The
holdfunctionmaybeusefulincaseswheretheSPIdataand
clock signals are shared with other devices. For example,
considerifthepagebufferwasonlypartiallywrittenwhena
priorityinterruptrequiresuseoftheSPIbus.Inthiscasethe
hold function can save the state of the instruction and the
data in the buffer so programming can resume where it left
off once the bus is available again.
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6
Toinitiateaholdcondition,thedevicemustbeselectedwith
CS low. A hold condition will activate on the falling edge of
the HOLD signal if the CLK signal is already low. If the CLK
is not already low the hold condition will activate after the
next falling edge of CLK. The hold condition will terminate
on the rising edge of the hold signal if the CLK signal is
alreadylow. IftheCLKisnotalreadylowtheholdcondition
will terminate after the next falling edge of CLK.
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Afterpower-upthedeviceinautomaticallyplacedinawrite-
disabled state with the Status Register Write Enable Latch
(WEL)settoa0.AWriteEnableinstructionmustbeissued
beforeaPageProgram, SectorErase, BulkEraseorWrite
Status Register instruction will be accepted. After complet-
ing a program, erase or write instruction the Write Enable
Latch(WEL)isautomaticallyclearedtoawrite-disabledstate
of 0.
8
Duringaholdcondition,theSerialDataOutput(DO)ishigh
impedance, and Serial Data Input (DI) and Serial Clock
(CLK) are ignored. The Chip Select (CS) signal should be
keptactive(low)forthefulldurationoftheholdoperationto
avoid resetting the internal logic state of the device.
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Software controlled write protection is facilitated using the
Write Status Register instruction and setting the Status
Register Protect (SRP) and Block Protect (BP0, BP2) bits.
These Status Register bits allow a portion or all of the
memorytobeconfiguredasreadonly.Usedinconjunction
with the Write Protect (WP) pin, changes to the Status
Registercanbeenabledordisabledunderhardwarecontrol.
See Status Register for further information.
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11
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WRITE PROTECTION
Applications that use non-volatile memory must take into
consideration the possibility of noise and other adverse
system conditions that may compromise data integrity. To
addressthisconcerntheNX25P10/20/40providesseveral
means to protect data from inadvertent writes.
Additionally, the Power-down instruction offers an extra
level of write protection as all instructions are ignored
except for the Release Power-down instruction.
NexFlashTechnologies, Inc.
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PRELIMINARY MKP-0009 Rev 6 NXSF040I-0405
04/04/05 ©