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All about Processor . Part 2

Control Signals

Control signals are electronic signals that orchestrate the various processor units participating in the execution of an instruction. Control signals are sent using an element called a sequencer. For example, the Read / Write signal allows the memory to be told that the processor wants to read or write information.
Functional Units

The processor is made up of a group of interrelated units (or control units). Microprocessor architecture varies considerably from one design to another, but the main elements of a microprocessor are as follows:

A control unit that links the incoming data, decodes it, and sends it to the execution unit:The control unit is made up of the following elements:
sequencer (or monitor and logic unit) that synchronizes instruction execution with the clock speed. It also sends control signals;
ordinal counter that contains the address of the instruction currently being executed;
instruction register that contains the following instruction.
An execution unit (or processing unit) that accomplishes tasks assigned to it by the instruction unit. The execution unit is made of the following elements:
The arithmetical and logic unit (written ALU). The ALU performs basic arithmetical calculations and logic functions (AND, OR, EXCLUSIVE OR, etc.);
The floating point unit (written FPU) that performs partial complex calculations which cannot be done by the arithmetical and logic unit.
The status register;
The accumulator register.
A bus management unit (or input-output unit) that manages the flow of incoming and outgoing information and that interfaces with system RAM;




The diagram below gives a simplified representation of the elements that make up the processor (the physical layout of the elements is different than their actual layout):

Transistor

To process information, the microprocessor has a group of instructions, called the "instruction set", made possible by electronic circuits. More precisely, the instruction set is made with the help of semiconductors, little "circuit switches" that use the transistor effect, discovered in 1947 by John Barden, Walter H. Brattain and William Shockley who received a Nobel Prize in 1956 for it.
A transistor (the contraction of transfer resistor) is an electronic semi-conductor component that has three electrodes and is capable of modifying current passing through it using one of its electrodes (called control electrode). These are referred to as "active components", in contrast to "passive components", such as resistance or capacitors which only have two electrodes (referred to as being "bipolar").
A MOS (metal, oxide, silicone) transistor is the most common type of transistor used to design integrated circuits. MOS transistors have two negatively charged areas, respectively called source (which has an almost zero charge) and drain (which has a 5V charge), separated by a positively charged region, called a substrate). The substrate has a control electrode overlaid, called a gate, that allows a charge to be applied to the substrate.
When there is no charge on the control electrode, the positively charged substrate acts as a barrier and prevents electron movement from the source to the drain. However, when a charge is applied to the gate, the positive charges of the substrate are repelled and a negatively charged communication channel is opened between the source and the drain.
 The transistor therefore acts as a programmable switch, thanks to the control electrode. When a charge is applied to the control electrode, it acts as a closed interrupter and, when there is no charge, it acts as an open interrupter.
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