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X25020PG-2.7 Datasheet(PDF) 3 Page - IC MICROSYSTEMS |
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X25020PG-2.7 Datasheet(HTML) 3 Page - IC MICROSYSTEMS |
3 / 14 page X25020 3 Status Register The RDSR instruction provides access to the status register. The status register may be read at any time, even during a write cycle. The status register is format- ted as follows: BP0 and BP1 are set by the WRSR instruction. WEL and WIP are read-only and automatically set by other operations. The Write-In-Process (WIP) bit indicates whether the X25020 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. During a write, all other bits are set to “1”. The Write Enable Latch (WEL) bit indicates the status of the “write enable” latch. When set to a “1”, the latch is set, when set to a “0”, the latch is reset. The Block Protect (BP0 and BP1) bits are nonvolatile and allow the user to select one of four levels of protec- tion. The X25020 is divided into four 512-bit segments. One, two, or all four of the segments may be protected. That is, the user may read the segments but will be unable to alter (write) data within the selected segments. The partitioning is controlled as illustrated below. Status Register Bits Array Addresses BP1 BP0 Protected 0 0 None 0 1 $C0–$FF 1 0 $80–$FF 1 1 $00–$FF 3834 PGM T03 Table 1. Instruction Set Instruction Name Instruction Format* Operation WREN 0000 0110 Set the Write Enable Latch (Enable Write Operations) WRDI 0000 0100 Reset the Write Enable Latch (Disable Write Operations) RDSR 0000 0101 Read Status Register WRSR 0000 0001 Write Status Register READ 0000 0011 Read Data from Memory Array beginning at selected address WRITE 0000 0010 Write Data to Memory Array beginning at Selected Address (1 to 32 Bytes) 3834 PGM T04 *Instructions are shown MSB in leftmost position. Instructions are transferred MSB first. 76 54 3 2 1 0 X X X X BP1 BP0 WEL WIP 3834 PGM T02 PRINCIPLES OF OPERATION The X25020 is a 256 x 8 E2PROM designed to interface directly with the synchronous serial peripheral interface (SPI) of many popular microcontroller families. The X25020 contains an 8-bit instruction register. It is accessed via the SI input, with data being clocked in on the rising SCK. CS must be LOW and the HOLD and WP inputs must be HIGH during the entire operation. Table 1 contains a list of the instructions and their opcodes. All instructions, addresses and data are trans- ferred MSB first. Data input is sampled on the first rising edge of SCK after CS goes LOW. SCK is static, allowing the user to stop the clock and then resume operations. If the clock line is shared with other peripheral devices on the SPI bus, the user can assert the HOLD input to place the X25020 into a “PAUSE” condition. After releasing HOLD, the X25020 will resume operation from the point when HOLD was first asserted. Write Enable Latch The X25020 contains a “write enable” latch. This latch must be SET before a write operation will be completed internally. The WREN instruction will set the latch and the WRDI instruction will reset the latch. This latch is automatically reset upon a power-up condition and after the completion of a byte, page, or status register write cycle. |
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