Glossary

Clean

A cache line that has not been modified while it is in the cache is said to be clean. To clean a

 

cache is to write dirty cache entries into main memory. If a cache line is clean, it is not written

 

on a cache miss because the next level of memory contains the same data as the cache.

 

See also Dirty.

Clock gating

Gating a clock signal for a macrocell with a control signal (such as PWRDOWN) and using the

 

modified clock that results to control the operating state of the macrocell.

Clocks Per Instruction (CPI)

 

See Cycles Per Instruction (CPI).

Coherency

See Memory coherency.

Cold reset

Also known as power-on reset. Starting the processor by turning power on. Turning power off

 

and then back on again clears main memory and many internal settings. Some program failures

 

can lock up the processor and require a cold reset to enable the system to be used again. In other

 

cases, only a warm reset is required.

See also Warm reset.

Communications channel

Software running on an ARM processor uses this to communicate with an external host through the debug interface. It can also be called the Debug Communications Channel. It is architecture-defined. See the ARM Architecture Reference Manual and your product technical reference manual for specific information.

Condition field

A 4-bit field in an instruction that is used to specify a condition under which the instruction can

 

execute.

Conditional execution

If the condition code flags indicate that the corresponding condition is true when the instruction

 

 

starts executing, it executes normally. Otherwise, the instruction does nothing.

Context

The environment that each process operates in for a multitasking operating system. In ARM

 

processors, this is limited to mean the physical address range that it can access in memory and

 

the associated memory access permissions.

 

See also Fast context switch.

Control bits

The bottom eight bits of a Program Status Register (PSR). The control bits change when an

 

exception arises and can be altered by software only when the processor is in a Privileged mode.

Coprocessor

A processor that supplements the main processor. It carries out additional functions that the

 

main processor cannot perform. Usually used for floating-point math calculations, signal

 

processing, or memory management.

Copy back

See Write-back.

Core module

In the context of an ARM Integrator, a core module is an add-on development board that

 

contains an ARM processor and local memory. Core modules can run standalone, or can be

 

stacked onto Integrator motherboards.

Core reset

See Warm reset.

CPI

See Cycles per instruction.

CPSR

See Current Program Status Register.

Current Program Status Register (CPSR)

The register that holds the current operating processor status.

ARM DDI 0363E

Copyright © 2009 ARM Limited. All rights reserved.

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ARM R4F, r1p3 manual See also Dirty