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10 page 
25AA128/25LC128 DS21831D-page 10 © 2009 Microchip Technology Inc. 2.5 Read Status Register Instruction (RDSR) The Read Status Register instruction (RDSR) provides access to the STATUS register. The STATUS register may be read at any time, even during a write cycle. The STATUS register is formatted as follows: TABLE 2-2: STATUS REGISTER The Write-In-Process (WIP) bit indicates whether the 25XX128 is busy with a write operation. When set to a ‘1’, a write is in progress, when set to a ‘0’, no write is in progress. This bit is read-only. The Write Enable Latch (WEL) bit indicates the status of the write enable latch and is read-only. When set to a ‘1’, the latch allows writes to the array, when set to a ‘0’, the latch prohibits writes to the array. The state of this bit can always be updated via the WREN or WRDI commands regardless of the state of write protection on the STATUS register. These commands are shown in Figure 2-4 and Figure 2-5. The Block Protection (BP0 and BP1) bits indicate which blocks are currently write-protected. These bits are set by the user issuing the WRSR instruction. These bits are nonvolatile, and are shown in Table 2-3. See Figure 2-6 for the RDSR timing sequence. FIGURE 2-6: READ STATUS REGISTER TIMING SEQUENCE (RDSR) 7 654 3 2 1 0 W/R ––– W/R W/R R R WPEN X X X BP1 BP0 WEL WIP W/R = writable/readable. R = read-only. SO SI CS 9 1011 12131415 11 0 0 0 0 00 76 5 4 2 1 0 Instruction Data from STATUS Register High-Impedance SCK 0 2 34 56 7 1 8 3 |
