8542 31 90: İşlemciler ve kontrolörler: diğerleri

This heading includes interchangeable pre-programmed memory modules in the form of a monolithic integrated circuit for electronic translation devices falling in subheadings 8470 10 00 and 8543 70 10.

This heading does not include discs (sometimes referred to as wafers) which, for the purposes of their applications in the field of electronics, consist of doped chemical elements, whether or not polished and whether or not epitaxially coated, provided that they have not been selectively doped or diffused to create discrete regions (heading 3818 00).

These subheadings include:

1. microprocessors, also called micro processing units (MPUs), which are integrated circuits that can be defined as devices that perform the primary instruction, execution and system control functions. They consist of the following main parts:

• the arithmetic logic unit (ALU);

• the instruction decoder and programme counter;

• the control unit;

• the input/output (I/O) unit, for communications with other devices.

A microprocessor can operate only if, apart from the internal memory, an external memory or other device is being used.

They may have one or more micro-program-memories (RAM or ROM) for loading or storing micro-instructions, thereby increasing the number of primary instructions in the control unit.

The micro-programmed ROM that a microprocessor may contain is dedicated to storing binary basic-instructions and is not to be considered as a real program memory storing the instructions to be executed.

These products may contain an instruction cache memory or micro-peripheral functions.

Microprocessors entirely processed for a specific application, based on ‘full custom’, ‘gate array’ or ‘standard cell’ designs, are included.

The processing capacity of microprocessors means the length of each word which the accumulator of the arithmetic and logic unit can process in a single micro-instruction cycle;

2. microcontrollers and microcomputers which are integrated circuits, consisting of at least the following main parts:

• a microprocessor, also called micro processing unit (MPU);

• a program memory (for example, RAM, ROM, PROM, EPROM, E2ROM, flash E2PROM) linked to the instruction decoder and containing a program defining an instruction sequence;

• a data memory (for example, RAM or E2PROM), not accessible from outside the chip contrary to microprocessors;

• an external bus (for data, addresses or instructions).

Microcontrollers are programmed, or further programmable, to perform specific functions and only for certain use (for example, for television receivers, video recording or reproducing apparatus or microwave ovens).

Microcomputers are capable of operating independently (stand alone) and for general use (for example, mainframes, minicomputers and personal computers). Microcomputers are freely programmable in accordance with the requirements of the user.

Microcontrollers, entirely processed for a specific application, based on ‘full custom’, ‘gate array’ or ‘standard cell’ designs, are included.

The processing capacity of microcontrollers or microcomputers means the length of each word which the accumulator of the arithmetic logic unit can process in a single micro-instruction cycle;

3. control circuits which are integrated circuits used to influence a process or the performance of a machine (for example, an automatic data-processing machine). Control circuits (for example, for disk storage units, memories, electric motors or cathode ray tubes) are generally capable of interpreting signals and, in accordance with the interpretation, determining the timing and sequence of certain functions (for example, input, processing, storage and output in an automatic data-processing system).