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X9520V20IZ-BT1 Datasheet(PDF) 11 Page - Intersil Corporation |
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X9520V20IZ-BT1 Datasheet(HTML) 11 Page - Intersil Corporation |
11 / 29 page 11 FN8206.2 August 20, 2007 EEPROM Array Read Operations Read operations are initiated in the same manner as write operations with the exception that the R/W bit of the Slave Address Byte is set to one. There are three basic read operations: Current EEPROM Address Read, Random EEPROM Read, and Sequential EEPROM Read. Current EEPROM Address Read Internally the device contains an address counter that maintains the address of the last word read incremented by one. Therefore, if the last read was to address n, the next read operation would access data from address n+1. On power-up, the address of the address counter is undefined, requiring a read or write operation for initialization. Upon receipt of the Slave Address Byte with the R/W bit set to one, the device issues an ACKNOWLEDGE and then transmits the eight bits of the Data Byte. The master terminates the read operation when it does not respond with an ACKNOWLEDGE during the ninth clock and then issues a STOP condition (See Figure 14 for the address, ACKNOWLEDGE, and data transfer sequence). It should be noted that the ninth clock cycle of the read operation is not a “don’t care.” To terminate a read operation, the master must either issue a STOP condition during the ninth cycle or hold SDA HIGH during the ninth clock cycle and then issue a STOP condition. Another important point to note regarding the “Current EEPROM Address Read” , is that this operation is not available if the last executed operation was an access to a DCP or the CONSTAT Register (i.e.: an operation using the Device Type Identifier 1010111 or 1010010). Immediately after an operation to a DCP or CONSTAT Register is performed, only a “Random EEPROM Read” is available. Immediately following a “Random EEPROM Read” , a “Current EEPROM Address Read” or “Sequential EEPROM Read” is once again available (assuming that no access to a DCP or CONSTAT Register occur in the interim). Random EEPROM Read Random read operation allows the master to access any memory location in the array. Prior to issuing the Slave Address Byte with the R/W bit set to one, the master must first perform a “dummy” write operation. The master issues the START condition and the Slave Address Byte, receives an ACKNOWLEDGE, then issues an Address Byte. This “dummy” Write operation sets the address pointer to the address from which to begin the random EEPROM read operation. After the X9520 acknowledges the receipt of the Address Byte, the master immediately issues another START condition and the Slave Address Byte with the R/W bit set to one. This is followed by an ACKNOWLEDGE from the X9520 and then by the eight bit word. The master terminates ADDRESS = 1110 5 bytes 7 BYTES ADDRESS = 610 ADDRESS POINTER ENDS HERE ADDRESS = 710 FIGURE 13. EXAMPLE: WRITING 12 BYTES TO A 16-BYTE PAGE STARTING AT LOCATION 11. 5 BYTES ADDRESS = 1510 S T A R T S T O P SLAVE ADDRESS DATA A C K SDA BUS SIGNALS FROM THE SLAVE SIGNALS FROM THE MASTER 1 FIGURE 14. CURRENT EEPROM ADDRESS READ SEQUENCE 1 0 0 0 0 0 1 X9520 |
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