Книга: Introduction to Microprocessors and Microcontrollers

The fetch–execute cycle

The fetch–execute cycle

This is the order of operations by a microprocessor and is the cause of all the confusion in the last paragraph.

The microprocessor applies no intelligence at all. It follows the pattern shown in Figure 8.11 regardless of whether it is following the program or it has been fed with a program with an error in it and is now carrying out a totally useless set of random instructions.

Figure 8.11 The fetch–execute cycle

It will follow our instructions so don’t blame the microprocessor – it’s up to us to feed it with something sensible. Always remember GIGO – garbage in, garbage out.

As we have seen, there is nothing inherently different between an instruction and data. They are both binary numbers and the interpretation is only a matter of what the microprocessor is expecting at that particular time.

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