If we start in the upper half of the schematics you will find components all microprocessors must have: a control unit, an arithmetic unit (AE in th picture), an different kinds of registers.
The control unit is built around a microcode program in most microprocessors. The microcode is stored in a rom. This has two advantages first a rom increase the ammount of logic which you can implement per square inch, second it is easy to upgrade the microcode within the rom to implement new features and bug fixes.
If we look to the right we will find the data and adress registers of the processor. The dataregisters are 8bit wide and the adressregisters are 16bits wide. Among the adress registers you can find registers such as PC(Program Counter), SP(Stack Pointer) and others. The program counter points to the memory adress of the next instruction for the microprocessor to perform and decode. The stack pointer points to the stack where the data and instructions are stored.
Furthermore you can find i/o registers which are used for the processorer to perform i/o operations directly without acessing the random acess memory. One examole of such an operation is a DMA(Direct Memory Acess operation).
Outside the dotted box you cand find the chips which are needed to make a complete computers systems.
-ROM and RAM chips
-UART chips for serial communication
-PIO chip for parallel communication
-DAC(Digital Analog Converter) chip, which converts signals between analog and digital form.
There also one chip micro computer chips where all of the above chips are integrated in order to fit a complete computer onto one single chip.
Writen by: Rikard Grossman-Nielsen
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