V22.0436 - Prof. Grishman

Lecture 24:  Input-Output:  Buses and I/O Transfers

Text, sections 6.5 and 6.6

Bus

A simple bus:  the ISA bus

Original bus of the IBM PC.
Includes the following signals (not a complete list)
The x86 has separate addresses spaces for memory and IO (port numbers);  some processors, such as MIPS, have a single address space for both (memory-mapped IO).

Control and Status Registers

Each I/O device is connected to the I/O bus through a controller. A simple controller will have at least 3 addresses (ports) on the bus, each corresponding to a register in the controller More complex devices (e.g., disks) will have multiple control and status registers

Controlling input-output transfers (section 6.6)