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CAT25C256Y20A-GT3 数据表(PDF) 7 Page - Catalyst Semiconductor |
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CAT25C256Y20A-GT3 数据表(HTML) 7 Page - Catalyst Semiconductor |
7 / 12 page 7 CAT25C128/256 Document No. 1018, Rev. I The WPEN (Write Protect Enable) is an enable bit for the WP pin. The WP pin and WPEN bit in the status register control the programmable hardware write protect fea- ture. Hardware write protection is enabled when WP is low and WPEN bit is set to high. The user cannot write to the status register (including the block protect bits and the WPEN bit) and the block protected sections in the memory array when the chip is hardware write pro- tected. Only the sections of the memory array that are not block protected can be written. Hardware write protection is disabled when either WP pin is high or the WPEN bit is zero. DEVICE OPERATION Write Enable and Disable The CAT25C128/256 contains a write enable latch. This latch must be set before any write operation. The device powers up in a write disable state when Vcc is applied. WREN instruction will enable writes (set the latch) to the device. WRDI instruction will disable writes (reset the latch) to the device. Disabling writes will protect the device against inadvertent writes. READ Sequence The part is selected by pulling CS low. The 8-bit read instruction is transmitted to the CAT25C128/256, followed by the 16-bit address(the three Most Significant Bit is don’t care for 25C256 and four most significant bits are don't care for 25C128). After the correct read instruction and address are sent, the data stored in the memory at the selected address is shifted out on the SO pin. The data stored in the memory at the next address can be read sequentially by continuing to provide clock pulses. The internal address pointer is automatically incremented to the next higher address after each byte of data is shifted out. When the highest address (7FFFh for 25C256 and 3FFFh for 25C128) is reached, the address counter rolls over to 0000h allowing the read cycle to be continued indefinitely. The readoperation is terminated by pulling the CS high. SK SI CS SO 00000 11 0 HIGH IMPEDANCE Figure 2. WREN Instruction Timing SK SI CS SO 00000 10 0 HIGH IMPEDANCE Note: Dashed Line= mode (1, 1) — — — — Figure 3. WRDI Instruction Timing |
类似零件编号 - CAT25C256Y20A-GT3 |
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类似说明 - CAT25C256Y20A-GT3 |
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