Processor is heart of embedded system

Why the processor is the heart of an embedded system

• It executes the program (firmware) that implements the product's function; nothing happens without it.
• It controls and coordinates every other part: memory, sensors, actuators and communication interfaces.
• It reads inputs, processes data and decides outputs in real time, as the heart pumps blood to the body.
• Its speed, word length, power and cost decide the performance, power use and cost of the whole system.
• Memory size, interfacing and software tools are chosen according to the processor.

Structural units of a processor

   +----------------------------------------+
   |  Control unit (PC, IR, decoder)        |
   |   |                                    |
   |  Datapath: registers <-> ALU           |
   |   |                                    |
   |  Bus interface / cache                 |
   +--------+-------------------------------+
            | address, data, control buses
         Memory and I/O

• Control unit (controller): program counter, instruction register, instruction decoder and timing/control logic that sequences operations.
• ALU (arithmetic logic unit): performs arithmetic and logic operations and sets flags.
• Registers: accumulator, general-purpose registers, status register, stack pointer, address registers; fast temporary storage.
• Internal buses and multiplexers: move data among the units.
• Bus interface unit / memory interface: address, data and control buses to external memory and I/O.
• Cache/on-chip memory and pipeline units (in advanced processors).