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Byte Addressability

Byte Addressability. Bytes are always 8 bits Word length typically ranges from 16 to 64 bits. Memory location assignments refer to successive byte locations in memory Memory is byte-accessible. For 8086, a Word is 16-bits (2 bytes). Word Length. For the 8086, a Word is 16-bits (2 bytes).

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Byte Addressability

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  1. Byte Addressability • Bytes are always 8 bits • Word length typically ranges from 16 to 64 bits. • Memory location assignments refer to successive byte locations in memory • Memory is byte-accessible. • For 8086, a Word is 16-bits (2 bytes)

  2. Word Length • For the 8086, a Word is 16-bits (2 bytes)

  3. Little-Endian Formatting • There are two ways that byte addresses can be assigned across words. • Big-Endian – higher byte addresses are used for the less significant bytes of a word • Little-Endian – lower byte addresses are used for the less significant bytes of a word • The Intel Architecture uses Little Endian

  4. Little-Endian Assignments • .data • List BYTE 10, 20, 30, 40, 50, 60 *note that with byte size data, there is no difference between Big-Endian and Little-Endian

  5. Big-Endian Assignments • .data • List BYTE 10, 20, 30, 40, 50, 60 *note that with byte size data, there is no difference between Big-Endian and Little-Endian

  6. Little-Endian Assignments • .data • List WORD 1020h, 3040h, 5060h *note that with word size data, the low-order byte is stored in a lower address

  7. Big-Endian Assignments • .data • List WORD 1020h, 3040h, 5060h *note that with word size data, the low-order byte is stored in a higher address

  8. Little-Endian Assignments • .data • List DWORD 10203040h, 50607080h *note that with word size data, the low-order byte is stored in a lower address

  9. Big-Endian Assignments • .data • List DWORD 10203040h, 50607080h *note that with word size data, the low-order byte is stored in a higher address

  10. Big-Endian Assignments • .data • List DWORD 00000006h *note that with word size data, the low-order byte is stored in a higher address

  11. Little-Endian Assignments • .data • List DWORD 00000006h *note that with word size data, the low-order byte is stored in a higher address

  12. Big-Endian Assignments • .data • List BYTE “This is a string”,0 *note: These are the ASCII values ‘T’=54H, ‘h’=68H, ‘ i’= 69H …

  13. Little-Endian Assignments • .data • List BYTE “This is a string”,0 *note: Strings are saved as byte data

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