Microcomputer | Electronic Control Unit (ECU) in Automobiles

Microcomputer | Electronic Control Unit (ECU) in Automobiles

1. Description
A microcomputer receives signals from input devices, processes those signals, and controls output devices.
At Toyota, a microcomputer is called an ECU (Electronic Control Unit).
In common on-vehicle systems, input devices are sensors, and output devices are actuators.

2. Construction
A microcomputer consists of a CPU (Central Processing Unit), various memory devices, and an I/O (input/output) interface.

Memory
Memory is comprised electric circuits that store programs to be operated or data to be exchanged.
There are two types of memory: ROM (Read-Only Memory), and RAM (Random Access Memory).
The ROM cannot be changed or deleted. Thus, the stored data will not disappear even if the power is turned off. For this reason, the ROM is used for storing programs that do not need to be changed or deleted.
The RAM is a type of memory in which data can be changed or deleted. Any data that is stored disappears when the power is turned off. Therefore, the RAM is used for storing data that can be changed or deleted through calculations performed by a CPU.

CPU
The CPU is the functional center of a computer that consists of a control device and a computing device.
It executes the commands that are ordered by a program accoding to the signals from the input devices, and controls the output devices.

I/O interface
An I/O interface converts the data from input devices into signals that can be identified by the CPU and memory.
In addition, it reconverts the CPU-processed data into signals that can be identified by the output devices.

Because the data transfer speeds of the I/O devices, CPU, and memory devices are different, one of the functions of an I/O interface is to adjust those speeds.