ST20-C1 datasheet(191/205 Pages) STMICROELECTRONICS

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Memory

Addressed devices which can be read and possibly written. Reading read/write

memory at a particular address gives the value that was last written to that

address. Reading read-only memory always gives the same value.

Memory-mapped

Addressed devices which are read and written as if they were

memory, but do not

necessarily return the last written value.

Microcode

The on-chip hardware mechanism for implementing instructions.

Micro-kernel

The ST20 on-chip hardware suppor t for multi-tasking.

MostNeg

The most negative 32-bit integer, #80000000. The address of the base of memory.

The value of the null process pointer

NotProcess.

Multi-tasking

Running several communicating

processes on the same processor using time

sharing.

Non-local

A non-local variable is one that is addressed by means of an offset from the base

address held in Areg. Non-local variables are usually not held on a stack and are

defined globally.

cf. local.

NotProcess

The null

process pointer, which has the value MostNeg.

On-chip emulator

Diagnostic controller unit.

On-chip memory

Very fast

memory included in the ST20 chip. On-chip memory is usually located at

the bottom of the

address space.

Operate

instruction component, with function code #F and mnemonic opr, used to

encode

secondary instructions. The instruction data value identifies the secondar y

instruction.

Operating system

Code controlling multi-tasking, interrupts and certain system operations, which

may be called by a program. The ST20 suppor ts many of these facilities in micro-

code without an operating system.

Operation

A secondary instruction.

Peripheral

A device connected to and controlled by the CPU.

ST20-C1 Datasheet(PDF) 191 Page - STMicroelectronics

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