Microprocessor-Logic of Digital Devices in Robotics

In this article we will throw some light on one of the very essential hardware components; the microprocessor. a microprocessor is a multipurpose programmable device which is fabricated on a single IC. It is used in almost every automatic machine nowadays. Microprocessors contain the logic of all the automatic machines. A list of instructions are executed inside the microprocessor and according to these instructions, microprocessor does the following three main functions.

Microprocessor uses its ALU to perform mathematical operations like addition, subtraction, multiplication and division. It can move data from one memory location to another.

A microprocessor can make decisions and jump to a new set of instructions.

Microprocessor has the following features: Address bus, Data bus, Read line, write line, Clock line and reset line.

Address bus: Address bus can be of 8,16,or 32 bit. It function is to send address to memory. Data bus: Data bus can also be 8, 16 or 32 bits. Its function is to send or receive the data from or to the memory.

RD/WR: The read and write line is used to tell the memory if he wants to set or get the addressed location.

Clock line: Clock line provides clock pulses to the processor.

Reset line: Reset line is used to reset the program counter and restart it for execution.

If we will take a look of its block-diagram. We can see a list of the features, ALU, program counter, Address latch, instruction register, instruction decoder, and with all of them some Tri-states buffers. We will see a test register and an instruction decoder is shown. The test register is a latch which holds the output which is given when ALU compares the two values. During the addition of two values the carry over value is stored in this test register. The output value stored in this test register is further given by instruction decoder. The instruction decoder uses the values to make decisions. Instruction register provides some control lines which directs all the buffers and latches and tell them what to do.

It tells the registers to latch the values on the data buses.

It tells the program counter to increment and latch the values which are currently on the data bus. Control lines not only instruct the program counter but also directs ALU to perform mathematical operations and test registers to latch the values from ALU. It also directs the Read and write lines to perform their functions. It is to be noted that any microprocessor has three essential features on the basis of which we can identify whether the microprocessor is powerful or not. These are: instruction set, Clock speed and Bandwidth. Instruction set is that set of instruction which a microprocessor can execute. Bandwidth means the number of bits which is executed in one instruction and clock pulse is the rate of executing information. It means the number of instruction executed in one second. Larger the value of their specifications more it will be powerful. Like 32-bit 25 MHz microprocessor will be more capable than 16-bit 20 MHz processor.

Let's try to know more about the features of a microprocessor; the ALU, Program counter etc.

The Program Counter is a register structure that contains the address pointer value of the current instruction. The value which is in the pointer, this value is read into the instruction decoder. Each cycle, the value at the pointer is read into the instruction decoder and the program counter is updated to point to the next instruction. The ALU is that part of the processor that performs mathematical functions in addition to the comparisons and bit shifting as well.

It works with accumulator and flag registers. The function of the accumulator is to hold the result of the performed operation. The Flag register contains a number of individual bits; these bits are used to store the results of the operation which is performed in last.

Addition and subtraction- Addition and subtractions are performed by half adders and full adders, for subtraction we can use the inverting operations.

Multiplication and division-For multiplication we use the floating-point hardware of processors, this can be found in advanced microprocessors.

Comparison-Comparison operation is used to compare values, like which one is greater or lesser or equal to each other. This can be done by subtracting one value from other.

Bit shifting-Shifting operations basically used to move bits left or right, this is made possible by using shift register, which uses pulses from the clock within the control unit. This is all about microprocessor and its features. This is a very essential hardware part of automatic machine. There are lots of advanced versions have been introduced nowadays with more and advanced features.


Microcontroller for robotics

555 timer IC in robotics