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EC24CXXXAR1GX Datasheet(PDF) 6 Page - E-CMOS Corporation |
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EC24CXXXAR1GX Datasheet(HTML) 6 Page - E-CMOS Corporation |
6 / 16 page EC24C128A/256A 128K/256K-bit 2-WIRE SERIAL CMOS EEPROM E-CMOS Corp. (www.ecmos.com.tw) Page 6 of 16 3I23N-Rev.F002 Device Addressing The 128K/256K EEPROM devices all require an 8-bit device address word following a start condition to enable the chip for a read or write operation (see to Figure 4). The device address word consists of a mandatory "1", "0" sequence for the first four most significant bits as shown. This is common to all the Serial EEPROM devices. The next 3 bits are the A2, A1 and A0 device address bits for the 128K/256K EEPROM. These 3 bits must compare to their corresponding hard-wired input pins. The A2, A1 and A0 pins use an internal proprietary circuit that biases them to a logic low condition if the pins are allowed to float. The eighth bit of the device address is the read/write operation select bit. A read operation is initiated if this bit is high and a write operation is initiated if this bit is low. Upon a compare of the device address, the EEPROM will output a "0". If a compare is not made, the chip will return to a standby state. DATA SECURITY: The EC24C128A /EC24C256A has a hardware data protection scheme that allows the user to write protect the entire memory when the WP pin is at VCC. Write Operations BYTE WRITE: A write operation requires an 8-bit data word address following the device address word and acknowledgment. Upon receipt of this address, the EEPROM will again respond with a "0" and then clock in the first 8-bit data word. Following receipt of the 8-bit data word, the EEPROM will output a "0" and the addressing device, such as a microcontroller, must terminate the write sequence with a stop condition. At this time the EEPROM enters an internally timed write cycle, tWR, to the nonvolatile memory. All inputs are disabled during this write cycle and the EEPROM will not respond until the write is complete (see to Figure 5). PAGE WRITE: The 128K/256K EEPROM is capable of an 64-byte page write. A page write is initiated the same as a byte write, but the microcontroller does not send a stop condition after the first data word is clocked in. Instead, after the EEPROM acknowledges receipt of the first data word, the microcontroller can transmit up to 63 (128K/256K) more data words. The EEPROM will respond with a "0" after each data word received. The microcontroller must terminate the page write sequence with a stop condition (see to Figure 6). The data word address lower six (128K/256K) bits are internally incremented following the receipt of each data word. The higher data word address bits are not incremented, retaining the memory page row location. When the word address, internally generated, reaches the page boundary, the following byte is placed at the beginning of the same page. If more than 64 data words are transmitted to the EEPROM, the data word address will "roll over" and previous data will be overwritten. ACKNOWLEDGE POLLING: Once the internally timed write cycle has started and the EEPROM inputs are disabled, acknowledge polling can be initiated. This involves sending a start condition followed by the device address word. The read/write bit is representative of the operation desired. Only if the internal write cycle has completed will the EEPROM respond with a "0", allowing the read or write sequence to continue. |
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