MPC8280 datasheet(1349/1386 Pages) FREESCALE

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MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

Glossary-5

Least-significant byte (LSB). Byte of least value in an address, register, data element, or

instruction encoding.

Little-endian. Byte-ordering method in memory where the address n of a word

corresponds to the least-significant byte. In an addressed memory word, the bytes

are ordered (left to right) 3, 2, 1, 0, with 3 being the most-significant byte. See

Big-endian.

Master. Name given to a bus device that has been granted control or mastership of the bus.

Memory access ordering. Specific order in which the processor performs load and store

memory accesses and the order in which those accesses complete.

Memory controller. Unit whose primary function is to control the external bus memories

and I/O devices.

Memory coherency. Aspect of caching in which it is ensured that an accurate view of

memory is provided to all devices that share system memory.

Memory consistency. Refers to agreement of levels of memory with respect to a single

processor and system memory (for example, on-chip cache, secondary cache, and

system memory).

Memory management unit (MMU). The functional unit that is capable of translating an

effective (logical) address to a physical address, providing protection

mechanisms, and defining caching methods.

Microarchitecture. The hardware details of a microprocessor’s design. Such details are

not defined by the PowerPC architecture.

Mnemonic. The abbreviated name of an instruction used for coding.

Modified state. When a cache block is in the modified state, it has been modified by the

processor since it was copied from memory. See MESI.

Munging. A modification performed on an effective address that allows it to appear to the

processor that individual aligned scalars are stored as little-endian values, when in

fact it is stored in big-endian order, but at different byte addresses within double

words. Note that munging affects only the effective address and not the byte order.

Note also that this term is not used by the PowerPC architecture.

Most-significant bit (msb). Highest-order bit in an address, registers, data element, or

instruction encoding.

Most-significant byte (MSB). Highest-order byte in an address, registers, data element, or

instruction encoding.

No-op. No-operation. A single-cycle operation that does not affect registers or generate bus

activity.

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