CY14MC256J_13 Datasheet, PDF (16/30 Pages) Cypress Semiconductor – 256-Kbit (32 K x 8) Serial (I2C) nvSRAM

CY14MC256J
CY14MB256J
CY14ME256J
By Master
SDA Line
By nvSRAM
Figure 28. Random Control Registers Multi-Byte Read
S
T
A
Control Registers
R
Slave Address
T
Control Register Address
Control Registers Slave Address
S 0 0 1 1 A2 A1 A0 0
Sr 0 0 1 1 A2 A1 A0 1
A
A
A
S
A
T
0
P
P
A
Data Byte
Data Byte N
Serial Number
Serial number is an 8 byte memory space provided to the user
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 user to utilize the eight byte memory
space in the desired format. The default values for the eight byte
locations are set to ‘0x00’.
Serial Number Write
The serial number can be accessed through the Control
Registers Slave Device. To write the serial number, master
transmits the Control Registers Slave address after the START
condition and writes to the address location from 0x01 to 0x08.
The content of Serial Number registers is secured to nonvolatile
memory on the next STORE operation. If AutoStore is enabled,
nvSRAM automatically stores the Serial number in the
nonvolatile memory on power-down. However, if AutoStore is
disabled, user must perform a STORE operation to secure the
contents of Serial Number registers.
Note If the serial number lock (SNL) bit is not set, the serial
number registers can be re-written regardless of whether or not
a STORE has happened. Once the serial number lock bit is set,
no writes to the serial number registers are allowed. If the master
tries to perform a write operation to the serial number registers
when the lock bit is set, a NACK is returned and write will not be
performed.
Serial Number Lock
After writes to Serial Number registers is complete, master is
responsible for locking the serial number by setting the serial
number lock bit to ‘1’ in the Memory Control Register (0x00). The
content of Memory Control Register and serial number are
secured on the next STORE operation (STORE or AutoStore). If
AutoStore is not enabled, user must perform STORE operation
to secure the lock bit status.
If a STORE was not performed, the serial number lock bit will not
survive power cycle. The serial number lock bit and 8 - byte serial
number is defaults to ‘0’ at power-up.
Serial Number Read
Serial number can be read back by a read operation of the
intended address of the Control Registers Slave. The Control
Registers Device loops back from the last address (excluding the
Command Register) to 0x00 address location while performing
burst read operation. The serial number resides in the locations
from 0x01 to 0x08. Even if the serial number is not locked, a
serial number read operation will return the current values written
to the serial number registers. Master may perform a serial
number read operation to confirm if the correct serial number is
written to the registers before setting the lock bit.
Document Number: 001-65233 Rev. *G
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