Specifications

Chapter 1 - Introduction to Microprocessors
Registers are therefore memory locations whose role is to help with performing various
mathematical operations or any other operations with data wherever data can be found. Look at
the current situation. We have two independent entities (memory and CPU) which are
interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for
example, we wish to add the contents of two memory locations and return the result again back
to memory, we would need a connection between memory and CPU. Simply stated, we must
have some "way" through data goes from one block to another.
1.3 Bus
That "way" is called "bus". Physically, it represents a group of 8, 16, or more wires
There are two types of buses: address and data bus. The first one consists of as many lines as
the amount of memory we wish to address, and the other one is as wide as data, in our case 8
bits or the connection line. First one serves to transmit address from CPU memory, and the
second to connect all blocks inside the microcontroller.
As far as functionality, the situation has improved, but a new problem has also appeared: we
have a unit that's capable of working by itself, but which does not have any contact with the
outside world, or with us! In order to remove this deficiency, let's add a block which contains
several memory locations whose one end is connected to the data bus, and the other has
connection with the output lines on the microcontroller which can be seen as pins on the
electronic component.
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