FM25V05 - 512Kb SPI FRAM
Unique Serial Number (FM25VN05 only)
The FM25VN05 device 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 serial number is read by issuing the SNR op-
code (C3h).
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
8-bit CRC
SN(63:56)
SN(55:48)
SN(47:40)
SN(39:32)
SN(31:24)
* Contact factory for requesting a customer identifier number.
SN(23:16)
SN(15:8)
SN(7:0)
Figure 14. 8-Byte Serial Number (read-only)
Function to Calculate CRC
BYTE calcCRC8( BYTE* pData, int nBytes )
{
static BYTE crctable[256] = {
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B,
0x38, 0x3F, 0x36, 0x31, 0x24, 0x23,
0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B,
0x48, 0x4F, 0x46, 0x41, 0x54, 0x53,
0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB,
0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3,
0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B,
0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3,
0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC,
0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4,
0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC,
0x8F, 0x88, 0x81, 0x86, 0x93, 0x94,
0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C,
0x1F, 0x18, 0x11, 0x16, 0x03, 0x04,
0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C,
0x6F, 0x68, 0x61, 0x66, 0x73, 0x74,
0x89, 0x8E, 0x87, 0x80, 0x95, 0x92,
0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA,
0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2,
0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA,
0x69, 0x6E, 0x67, 0x60, 0x75, 0x72,
0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A,
0x19, 0x1E, 0x17, 0x10, 0x05, 0x02,
0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A,
0x4E, 0x49, 0x40, 0x47, 0x52, 0x55,
0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D,
0x3E, 0x39, 0x30, 0x37, 0x22, 0x25,
0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D,
0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5,
0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D,
0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5,
0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD,
};
0x12,
0x2A,
0x62,
0x5A,
0xF2,
0xCA,
0x82,
0xBA,
0xD5,
0xED,
0xA5,
0x9D,
0x35,
0x0D,
0x45,
0x7D,
0x9B,
0xA3,
0xEB,
0xD3,
0x7B,
0x43,
0x0B,
0x33,
0x5C,
0x64,
0x2C,
0x14,
0xBC,
0x84,
0xCC,
0xF4,
0x15,
0x2D,
0x65,
0x5D,
0xF5,
0xCD,
0x85,
0xBD,
0xD2,
0xEA,
0xA2,
0x9A,
0x32,
0x0A,
0x42,
0x7A,
0x9C,
0xA4,
0xEC,
0xD4,
0x7C,
0x44,
0x0C,
0x34,
0x5B,
0x63,
0x2B,
0x13,
0xBB,
0x83,
0xCB,
0xF3
BYTE crc = 0;
while( nBytes-- ) crc = crctable[crc ^ *pData++];
return crc;
}
Rev. 2.0
May 2010
Page 10 of 16
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
