FM24V02 - 256Kb I2C FRAM
two bits are ‘Don’t care’ values. Only one
device must acknowledge this byte (the one
that has the I2C-bus slave address).
Unique Serial Number (FM24VN02 only)
The FM24VN02 device also incorporates a read-only
8-byte serial number. It can be used to uniquely
identify a pc board or system. The serial number
includes a 40-bit unique number, an 8-bit CRC, and a
16-bit number that can be defined upon request by
the customer. If a customer-specific number is not
requested, the 16-bit Customer Identifier is 0x0000.
The 8 bytes of data are accessed via a Slave Address
sequence similar to the Device ID. The serial number
can be read by the system as follows:
4. The master sends a Re-START command
5. The master sends Reserved Slave ID 0xCD to
read the serial number.
6. The master ends the serial number read
sequence by NACKing the last byte, thus
resetting the slave device state machine and
allowing the master to send the STOP
command.
The 8-bit CRC value can be used to compare to the
value calculated by the controller. If the two values
match, then the communication between slave and
master was performed without errors.
1. The master sends a START command
2. The master sends Reserved Slave ID 0xF8
3. The master sends the I2C-bus slave address of
the slave device it needs to identify. The last
CUSTOMER IDENTIFIER *
40-bit UNIQUE NUMBER
SN(39:32) SN(31:24) SN(23:16)
* Contact factory for requesting a customer identifier number.
8-bit CRC
SN(63:56)
SN(55:48)
SN(47:40)
SN(15:8)
SN(7:0)
Figure 15. 8-Byte Serial Number (read-only)
Start
S
No
Acknowledge
Address
A
Address
Start
Acknowledge
By Master
Stop
Rsvd Slave ID (F8)
Slave Address
A
S
Rsvd Slave ID (CD)
A
Data Byte 7
A
A
Data Byte 0
1
P
By FM24VN05
Acknowledge
Data
Figure 16. Read Serial Number
Rev. 0.1
Mar. 2009
Page 10 of 15
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