CY14C064PA_12 Datasheet, PDF (18/43 Pages) Cypress Semiconductor – 64-Kbit (8 K × 8) SPI nvSRAM with Real Time Clock

CY14C064PA
CY14B064PA
CY14E064PA
instance when SLEEP instruction is registered. The device is not
accessible for normal operations after SLEEP instruction is
issued. Once in sleep mode, the SCK and SI pins are ignored
and SO will be Hi-Z but device continues to monitor the CS pin.
To wake the nvSRAM from the sleep mode, the device must be
selected by toggling the CS pin from HIGH to LOW. The device
wakes up and is accessible for normal operations after t_WAKE
duration after a falling edge of CS pin is detected.
Note Whenever nvSRAM enters into sleep mode, it initiates
nonvolatile STORE cycle which results in an endurance cycle per
sleep command execution. A STORE cycle starts only if a write
to the SRAM has been performed since the last STORE or
RECALL cycle.
CS
SCK
SI
SO
Figure 23. Sleep Mode Entry
tSLEEP
01234567
1011100 1
HI-Z
Serial Number
The serial number is an 8-byte programmable memory space
provided to you to uniquely identify this device. It typically
consists of a two byte Customer ID, followed by five bytes of
unique serial number and one byte of CRC check. However,
nvSRAM does not calculate the CRC and it is up to the system
designer to utilize the eight byte memory space in whatever
manner desired. The default value for eight byte locations are set
to ‘0x00’.
WRSN (Serial Number Write) Instruction
The serial number can be written using the WRSN instruction. To
write serial number the write must be enabled using the WREN
instruction. The WRSN instruction can be used in burst mode to
write all the 8 bytes of serial number.
The serial number is locked using the SNL bit of the Status
Register. Once this bit is set to '1', no modification to the serial
number is possible. After the SNL bit is set to '1', using the WRSN
instruction has no effect on the serial number.
A STORE operation (AutoStore or Software STORE) is required
to store the serial number in nonvolatile memory. If AutoStore is
disabled, you must perform a Software STORE operation to
secure and lock the serial number. If SNL bit is set to ‘1’ and is
not stored (AutoStore disabled), the SNL bit and serial number
defaults to ‘0’ at the next power cycle. If SNL bit is set to ‘1’ and
is stored, the SNL bit can never be cleared to ‘0’. This instruction
requires the WEN bit to be set before it can be executed. The
WEN bit is reset to '0' after completion of this instruction.
CS
SCK
SI
SO
Figure 24. WRSN Instruction
0 1 2 34 5 67 0 1 23 4 56 7
56 57 58 59 60 61 62 63
11
Op-Code
Byte - 8
Byte - 1
0 0 0 0 1 0 D7 ^{D6 D5 D4 D3 D2 D1 D0}
D7 D6 D5 D4 D3 D2 D1 D0
MSB
LSB
8-Byte Serial Number
HI-Z
Document Number: 001-68249 Rev. *C
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