
PROGRAMMING CONCEPTS – IV 193
KEY POINTS OF THIS CHAPTER
In the use of an input port, RD is the control signal of importance. The machine cycle initiated is
the I/O Read machine cycle.
In the use of an output port, WR is the control signal of importance. The machine cycle initiated is
the I/O. Write machine cycle.
An I/O port can have 8 or 16 as the width of its data bus.
An I/O port can have 8 or 16 as the width of its address bus.
There are two schemes for I/O interfacing i.e., memory mapped I/O and I/O mapped I/O.
There are two types I/O addressing – xed port and variable port.
If the address is 8 bits, xed port addressing is to ...