Introduction
 

  • Remainding topics in computer architecture:

      • How do the different devices inside the computer communicate with each other ?

  • Topics discussed next:

      1. How the CPU communicates (READ/WRITE) with the (relatively fast) memory (RAM)

      2. How the CPU communicates (READ/WRITE) with the (very slow) IO devices

Review: the memory read operation

The simplified presentation of the read operation:

 

CPU sends address and a READ command
The memory sends back the data on the databus and the CPU stores it in its MDR register

Review: the memory write operation

The simplified presentation of the write operation:

 

CPU sends address, data and a WRITE command
The memory stores the data away.

Making components from different manufacturers work together

A big problem is heterogeneity:

 

Products from different manufacturers may not work with each other !!!

Making components from different manufacturers work together
 

  • In order to ensure compatibility all devices inside the computer must follow (= obey) a strick set of rules

  • This set of rules is called a bus protocol (because it specify the rules (= protocol) for the bus that connect the communicating devices)

  • In the bus protocol, the communicating devices will exchange signals according to the rules defined by the bus protocol

 

 

We will first look at what kind of signals are sent over the wires in a bus....