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24AA025 Datasheet(PDF) 8 Page - Microchip Technology |
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24AA025 Datasheet(HTML) 8 Page - Microchip Technology |
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8 / 26 page  24AA024/24LC024/24AA025/24LC025 DS21210K-page 8 © 2007 Microchip Technology Inc. 6.0 WRITE OPERATIONS 6.1 Byte Write Following the Start signal from the master, the device code(4 bits), the Chip Select bits (3 bits) and the R/W bit (which is a logic-low) is placed onto the bus by the master transmitter. The device will acknowledge this control byte during the ninth clock pulse. The next byte transmitted by the master is the word address and will be written into the Address Pointer of the 24AA024/ 24LC024/24AA025/24LC025. After receiving another Acknowledge signal from the 24AA024/24LC024/ 24AA025/24LC025, the master device will transmit the data word to be written into the addressed memory location. The 24AA024/24LC024/24AA025/24LC025 acknowledges again and the master generates a Stop condition. This initiates the internal write cycle and, dur- ing this time, the 24AA024/24LC024/24AA025/ 24LC025 will not generate Acknowledge signals (Figure 6-1). If an attempt is made to write to the protected portion of the array when the hardware write protection (24XX024 only) has been enabled, the device will acknowledge the command, but no data will be written. The write cycle time must be observed even if write protection is enabled. 6.2 Page Write The write control byte, word address and the first data byte are transmitted to the 24AA024/24LC024/ 24AA025/24LC025 in the same way as in a byte write. However, instead of generating a Stop condition, the master transmits up to 15 additional data bytes to the 24AA024/24LC024/24AA025/24LC025, which are temporarily stored in the on-chip page buffer and will be written into the memory once the master has transmit- ted a Stop condition. Upon receipt of each word, the four lower-order Address Pointer bits are internally incremented by one. The higher-order four bits of the word address remain constant. If the master should transmit more than 16 bytes prior to generating the Stop condition, the address counter will roll over and the previously received data will be overwritten. As with the byte-write operation, once the Stop condition is received, an internal write cycle will begin (Figure 6-2). If an attempt is made to write to the protected portion of the array when the hardware write protection has been enabled, the device will acknowledge the command, but no data will be written. The write cycle time must be observed even if write protection is enabled. 6.3 Write Protection The WP pin (available on 24XX024 only) must be tied to VCC or VSS. If tied to VCC, the entire array will be write-protected. If the WP pin is tied to VSS, write operations to all address locations are allowed. FIGURE 6-1: BYTE WRITE FIGURE 6-2: PAGE WRITE Note: Page write operations are limited to writing bytes within a single physical page, regardless of the number of bytes actually being written. Physical page boundaries start at addresses that are integer multiples of the page buffer size (or ‘page size’) and end at addresses that are integer multiples of [page size – 1]. If a Page Write command attempts to write across a physical page boundary, the result is that the data wraps around to the beginning of the current page (overwriting data previously stored there), instead of being written to the next page, as might be expected. It is therefore necessary for the application software to prevent page write operations that would attempt to cross a page boundary. S P BUS ACTIVITY MASTER SDA LINE BUS ACTIVITY S T A R T S T O P Control Byte Word Address Data A C K A C K A C K S P BUS ACTIVITY MASTER SDA LINE BUS ACTIVITY S T A R T Control Byte Word Address (n) Data (n) Data (n + 15) S T O P A C K A C K A C K A C K A C K Data (n +1) |
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Similar Description - 24AA025 |
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