FM24V10 - 1Mb I2C FRAM

Document Number: 001-84463 Rev. **

Page 10 of 17

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 I

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 I

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. 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)

SN(23:16)

SN(15:8)

SN(7:0)

* Contact factory for requesting a customer identifier number.

Figure 15. 8-Byte Serial Number (read-only)

S

A

Data Byte 7

1

P

By Master

By FM24VN10

Start

Address

Stop

No

Acknowledge

Data

S

A

Rsvd Slave ID (F8)

Slave Address

A

Start

Address

Acknowledge

Rsvd Slave ID (CD)

A

A

Data Byte 0

Acknowledge

X X

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,

0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,