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M29DW640F70N6E Datasheet(PDF) 65 Page - Numonyx B.V |
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M29DW640F70N6E Datasheet(HTML) 65 Page - Numonyx B.V |
65 / 74 page M29DW640F Extended Memory Block 65/74 Appendix C Extended Memory Block The has an extra block, the Extended Block, that can be accessed using a dedicated command. This Extended Block is 128 Words in x16 mode and 256 Bytes in x8 mode. It is used as a security block (to provide a permanent security identification number) or to store additional information. The Extended Block is either Factory Locked or Customer Lockable, its status is indicated by bit DQ7. This bit is permanently set to either ‘1’ or ‘0’ at the factory and cannot be changed. When set to ‘1’, it indicates that the device is factory locked and the Extended Block is protected. When set to ‘0’, it indicates that the device is customer lockable and the Extended Block is unprotected. Bit DQ7 being permanently locked to either ‘1’ or ‘0’ is another security feature which ensures that a customer lockable device cannot be used instead of a factory locked one. Bit DQ7 is the most significant bit in the Extended Block Verify Code and a specific procedure must be followed to read it. See “Extended Block Indicator Bit” in Table 4: Bus operations, BYTE = VIL and Table 5: Bus operations, BYTE = VIH, respectively, for details of how to read bit DQ7. The Extended Block can only be accessed when the device is in Extended Block mode. For details of how the Extended Block mode is entered and exited, refer to Section 4.3: Block Protection commands and Section 4.3.2: Exit Extended Block command, and to Table 6: Commands, 16-bit mode, BYTE = VIH and Table 7: Commands, 8-bit mode, BYTE = VIL, respectively. C.1 Factory Locked Extended Block In devices where the Extended Block is factory locked, the Security Identification Number is written to the Extended Block address space (see Table 31: Extended Block address and data) in the factory. The DQ7 bit is set to ‘1’ and the Extended Block cannot be unprotected. C.2 Customer Lockable Extended Block A device where the Extended Block is customer lockable is delivered with the DQ7 bit set to ‘0’ and the Extended Block unprotected. It is up to the customer to program and protect the Extended Block but care must be taken because the protection of the Extended Block is not reversible. There are two ways of protecting the Extended Block: ● Issue the Enter Extended Block command to place the device in Extended Block mode, then use the In-System Technique with RP either at VIH or at VID (refer to Appendix D, Figure 22: In-System Equipment Group Protect flowchart and Figure 23: In-System Equipment Chip Unprotect flowchart, for a detailed explanation of the technique). ● Issue the Enter Extended Block command to place the device in Extended Block mode, then use the Programmer Technique (refer to Appendix D, Figure 20: Programmer Equipment Group Protect flowchart and Figure 21: Programmer Equipment Chip Unprotect flowchart, for a detailed explanation of the technique). |
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