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X55060 Datasheet(PDF) 11 Page - Intersil Corporation |
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X55060 Datasheet(HTML) 11 Page - Intersil Corporation |
11 / 23 page 11 FN8133.0 March 28, 2005 When WP is HIGH, all functions, including nonvolatile writes to the Status Register operate normally. Setting the WPEN bit in the Status Register to “0” blocks the WP pin function, allowing writes to the Status Register when WP is HIGH or LOW. Setting the WPEN bit to “1” while the WP pin is LOW activates the Programma- ble ROM mode, thus requiring a change in the WP pin prior to subsequent Status Register changes. This allows manufacturing to install the device in a system with WP pin grounded and still be able to program the Status Register. Manufacturing can then load Configu- ration data, manufacturing time and other parameters into the EEPROM, then set the portion of memory to be protected by setting the block lock bits, and finally set the “OTP mode” by setting the WPEN bit. Data changes to protected areas of the device now require a hardware change. Read Sequence When reading from the EEPROM memory array, CS is first pulled low to select the device. The 8-bit READ instruction is transmitted to the device, followed by the 16-bit address. After the READ opcode and address are sent, the data stored in the memory at the selected address is shifted out on the SO line. The data stored in memory at the next address can be read sequentially by continuing to provide clock pulses. The address is automatically incremented to the next higher address after each byte of data is shifted out. The read operation is terminated by taking CS high. Refer to the Read EEPROM Array Sequence (Figure 7). To read the Status Register, the CS line is first pulled low to select the device followed by the 8-bit RDSR instruction. After the RDSR opcode is sent, the contents of the Status Register are shifted out on the SO line. Refer to the Read Status Register Sequence (Figure 8). Refer to the Serial Output Timing on page 18. Write Sequence Prior to any attempt to write data into the device, the “Write Enable” Latch (WEL) must first be set by issu- ing the WREN instruction (Figure 9). CS is first taken LOW, then the WREN instruction is clocked into the device. After all eight bits of the instruction are trans- mitted, CS must then be taken HIGH. If the user con- tinues the Write Operation without taking CS HIGH after issuing the WREN instruction, the Write Opera- tion will be ignored. To write data to the EEPROM memory array, the user then issues the WRITE instruction followed by the 16 bit address and then the data to be written. Any unused address bits are specified to be “0’s”. The WRITE operation minimally takes 32 clocks. CS must go low and remain low for the duration of the opera- tion. If the address counter reaches the end of a page and the clock continues, the counter will roll back to the first address of the page and overwrite any data that may have been previously written. For the Page Write Operation (byte or page write) to be completed, CS can only be brought HIGH after bit 0 of the last data byte to be written is clocked in. If it is brought HIGH at any other time, the write operation will not be completed (Figure 10). To write to the Status Register, the WRSR instruction is followed by the data to be written (Figure 11). While the write is in progress following a Status Regis- ter or EEPROM Sequence, the Status Register may be read to check the WIP bit. During this time the WIP bit will be high. Refer to Serial Input timing on page 17. OPERATIONAL NOTES The device powers-up in the following state: – The device is in the low power standby state. – A HIGH to LOW transition on CS is required to enter an active state and receive an instruction. – SO pin is high impedance. – The Write Enable Latch is reset. – Reset Signal is active for tPURST. Data Protection The following circuitry has been included to prevent inadvertent writes: – A WREN instruction must be issued to set the Write Enable Latch. – A valid write command and address must be sent to the device. –CS must come HIGH after a multiple of 8 data bits in order to start a nonvolatile write cycle. X55060 |
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