What are busses?

Busses are collections of wires through which data is transmitted from one of sources to destinations

• data-bus
• address-buss
• control-bus -> Read, write, turn on, turn off, first n bits, last n bits

Why do we have busses?

Busses allow us to connect several sources to several destinations (routing), therefore minimising the needed number of physical connections.

Characteristics

• Bus width (bits)
  • How much data can be transmitted at a time
• Clock speed (MHz)
  • How often data can be transferred on the busses

Input Interface

Tri-state gates to select which interfaces are disabled.
So that only one interface will be enabled

74LS139 Decoder takes in 2 pins (A1,A0)

O0, O1, O2, O3 turned on/off depending on the values of A1 and A0

CPU Timing

Address bus WRITE, data bus write, WRITE signal

Set Register

ser -> Set all bits to 1

DDRA -> All 1 bits are OUTPUTs INPUT -> PIN OUTPUT -> PORT