FM24V10 Datasheet, PDF (10/16 Pages) Ramtron International Corporation – 1Mb Serial 3V F-RAM Memory

Unique Serial Number (FM24VN10 only)
The FM24VN10 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:
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
two bits are ‘Don’t care’ values. Only one
device must acknowledge this byte (the one
that has the I²C-bus slave address).
4. The master sends a Re-START command
FM24V10 - 1Mb I2C FRAM
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. The function
(shown below) is used to calculate the CRC value.
To perform the calculation, 7 bytes of data are
filled into a memory buffer in the same order as
they are read from the part – i.e. byte7, byte6,
byte5, byte4, byte3, byte2, byte1 of the serial
number. The calculation is performed on the 7
bytes, and the result should match the final byte out
from the part which is byte0, the 8-bit CRC value.
CUSTOMER IDENTIFIER *
40-bit UNIQUE NUMBER
SN(63:56) SN(55:48) SN(47:40) SN(39:32) SN(31:24) SN(23:16)
* Contact factory for requesting a customer identifier number.
Figure 15. 8-Byte Serial Number (read-only)
SN(15:8)
8-bit CRC
SN(7:0)
Start
By Master
Address
Start
Address
S Rsvd Slave ID (F8) A Slave Address X X A S Rsvd Slave ID (CD) A
Data Byte 7
Acknowledge
A
A
No
Acknowledge
Stop
Data Byte 0
1P
By FM24VN10
Acknowledge
Data
Figure 16. Read Serial Number
Function to Calculate CRC
BYTE calcCRC8( BYTE* pData, int nBytes )
{
static BYTE crctable[256] = {
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15,
0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,
0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,
0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,
0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5,
0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,
0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,
0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2,
0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,
0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,
0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,
0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,
0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,
0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,
Rev. 3.0
Jan. 2012
Page 10 of 16