PMC-Sierra Pm25LV512 User Manual
Page 9
9
Programmable Microelectronics Corp.
Issue Date: February, 2004, Rev: 1.4
PMC
Pm25LV512/010
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Table 6. WPEN Operation
The WRSR instruction also allows the user to enable or disable the Write Protect (WP#) pin through the use of the
Write Protect Enable (WPEN) bit. Hardware write protection is enabled when the WP# pin is low and the WPEN bit
is "1". Hardware write protection is disabled when either the WP# pin is high or the WPEN bit is "0." When the
device is hardware write protected, writes to the Status Register, including the Block Protect bits and the WPEN
bit, and the locked-out blocks in the memory array are disabled. Write is only allowed to blocks of the memory
which are not locked out. The WRSR instruction is self-timed to automatically erase and program BP0, BP1, and
WPEN bits. In order to write the status register, the device must first be write enabled via the WREN instruction.
Then, the instruction and data for the three bits are entered. During the internal write cycle, all instructions will be
ignored except RDSR instructions. The Pm25LV512/010 will automatically return to write disable state at the
completion of the WRSR cycle.
Note: When the WPEN bit is hardware write protected, it cannot be changed back to "0", as long as the WP# pin
is held low.
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Table 5. Block Write Protect Bits