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FM24V02-GTR 데이터시트(PDF) 10 Page - Cypress Semiconductor |
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FM24V02-GTR 데이터시트(HTML) 10 Page - Cypress Semiconductor |
10 / 16 page FM24V02 - 256Kb I2C FRAM Rev. 3.0 Jan. 2012 Page 10 of 16 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: 1. The master sends a START command 2. The master sends Reserved Slave ID 0xF8 3. The master sends the I 2C-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 I 2C-bus slave address). 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 FM24VN02 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 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, |
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