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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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FM25V40 датащи(PDF) 8 Page - Cypress Semiconductor |
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FM25V40 датащи(HTML) 8 Page - Cypress Semiconductor |
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8 / 23 page  PRELIMINARY FM25V40 Document Number: 001-87288 Rev. *A Page 8 of 23 RDSR - Read Status Register The RDSR command allows the bus master to verify the contents of the Status Register. Reading the status register provides information about the current state of the write-protection features. Following the RDSR opcode, the FM25V40 will return one byte with the contents of the Status Register. WRSR - Write Status Register The WRSR command allows the SPI bus master to write into the Status Register and change the write protect configuration by setting the WPEN, BP0 and BP1 bits as required. Before issuing a WRSR command, the WP pin must be HIGH or inactive. Note that on the FM25V40, WP only prevents writing to the Status Register, not the memory array. Before sending the WRSR command, the user must send a WREN command to enable writes. Executing a WRSR command is a write operation and therefore, clears the Write Enable Latch. Memory Operation The SPI interface, which is capable of a high clock frequency, highlights the fast write capability of the F-RAM technology. Unlike serial flash and EEPROMs, the FM25V40 can perform sequential writes at bus speed. No page register is needed and any number of sequential writes may be performed. Write Operation All writes to the memory begin with a WREN opcode with CS being asserted and deasserted. The next opcode is WRITE. The WRITE opcode is followed by a three-byte address containing the 19-bit address (A18-A0) of the first data byte to be written into the memory. The upper five bits of the three-byte address are ignored. Subsequent bytes are data bytes, which are written sequentially. Addresses are incremented internally as long as the bus master continues to issue clocks and keeps CS LOW. If the last address of 7FFFFh is reached, the counter will roll over to 00000h. Data is written MSB first. The rising edge of CS terminates a write operation. A write operation is shown in Figure 11. Note When a burst write reaches a protected block address, the automatic address increment stops and all the subsequent data bytes received for write will be ignored by the device. EEPROMs use page buffers to increase their write throughput. This compensates for the technology's inherently slow write operations. F-RAM memories do not have page buffers because each byte is written to the F-RAM array immediately after it is clocked in (after the eighth clock). This allows any number of bytes to be written without page buffer delays. Note If the power is lost in the middle of the write operation, only the last completed byte will be written. Figure 9. RDSR Bus Configuration Figure 10. WRSR Bus Configuration (WREN not shown) CS SCK SO 01234567 SI 00 0 0 0 1 0 0 1 HI-Z 0 12345 6 7 LSB D0 D1 D2 D3 D4 D5 D6 MSB D7 Opcode Data CS SCK SO 0 1 2 3 4567 SI 00 00 0 0 0 1 MSB LSB D2 D3 D7 HI-Z 0 12345 67 Opcode Data X X X X X |
Аналогичный номер детали - FM25V40 |
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Аналогичное описание - FM25V40 |
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