Datenblatt-Suchmaschine für elektronische Bauteile |
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FM25C640UE Datenblatt(PDF) 8 Page - Fairchild Semiconductor |
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FM25C640UE Datenblatt(HTML) 8 Page - Fairchild Semiconductor |
8 / 11 page 8 www.fairchildsemi.com FM25C640U Rev. B Bit0 (/RDY) indicates the Busy/Ready status of the EEPROM. This bit is a read-only bit and is read by executing RDSR instruction. If this bit is “1” then the EEPROM is busy doing a program cycle. If this bit is “0” then the EEPROM is ready. Note that if a RDSR instruction is executed when an internal programming cycle is in progress, only the /RDY bit is valid. All other bits are don’t cares. The RDSR command requires the following sequence. The /CS pin is pulled low to select the EEPROM and then the RDSR opcode is transmitted on the SI pin. After this is done, data on the SI pin becomes don’t care. The data from the Status Register is then shifted out on the SO pin starting with D7 bit first and D0 last. See Figure 6. FIGURE 6. Read Status Register WRITE SEQUENCE (WRITE): Write to the array is enabled only when /WP pin is held high and the EEPROM is write enabled previously (via WREN instruction). Also, the address of the memory location(s) to be programmed must be outside the protected address field selected by the Block Write Protection Level. See Table 4. TABLE 4. Block Write Protection Levels Level Status Register Bits Array Address BP1 BP0 Protected 0 0 0 None 1 0 1 1800-1FFF 2 1 0 1000-1FFF 3 1 1 0000-1FFF A WRITE command requires the following sequence. The /CS pin is pulled llow to select the EEPROM, then the WRITE opcode is transmitted on the SI pin followed by two bytes of address, "High byte addr" (A15-A8) and "Low byte addr" (A7-A0), further followed by the data (D7-D0) to be written. See Figure 9. Note that only A12- A0 address bits are treated valid by FM25C640U while bits A15- A13 are ignored. FIGURE 9. Byte Write /CS SI SO RDSR OP-CODE RDSR DATA WRITE ENABLE (WREN): When V CC is applied to the EEPROM, it “powers up” in a write- disabled state. Therefore, all programming modes (Write to memory array and Status register), must be preceded by a WRITE EN- ABLE (WREN) instruction. See Figure 7. FIGURE 7. Write Enable /CS SI SO WREN Op-Code WRITE DISABLE (WRDI): Executing this instruction disables all programming modes (Write to memory array and Status register), preventing the EEPROM from accidental writes. Once WRDI instruction is executed, WREN instruction should be executed to re-enable all program- ming modes. See Figure 8. FIGURE 8. Write Disable /CS SI SO WRDI Op-Code ;;;; CS SI SO Write Opcode High Addr Byte Low Addr Byte Data High Z Internally, the programming will start after the /CS pin is brought back to a high level. Note that the LOW to HIGH transition of the /CS pin must occur during the SCK low time immediately after clocking in the D0 data bit. See Figure 10. FIGURE 10. Start of Programming SCK SI SO /CS D0 D1 D2 High Z Start of internal programming Programming status (Busy/Ready) of the EEPROM can be deter- mined by executing a READ STATUS REGISTER (RDSR) in- struction after a write command. Upon executing the RDSR instruction, if Bit 0 of the RDSR data is “1”, it indicates the WRITE cycle is still in progress. If it is “0” then the WRITE cycle has ended. Note that while the internal programming is still in progress (Bit 0 = 1), only the RDSR instruction is enabled. It is recommended that no other instruction be issued till the internal programming is complete. |
Ähnliche Teilenummer - FM25C640UE |
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Ähnliche Beschreibung - FM25C640UE |
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