Microprocessor and Microcontrollers (CSE-3501) Lecture-2

1. Microprocessor and Microcontrollers (CSE-3501)Lecture-2 Instructor: SazidZaman Khan Lecturer, Department of Computer Science and Engineering, IIUC

2. Microprocessor based personal computer system Connected by Buses Memory System (RAMs CACHE. ROM) Microprocessor Input/output System (Printer, hard disk, mouse, monitor, DVD, etc) Figure-1: Microprocessor based Computer System [Fig-1-6 [Barry b. Bray-8th edition, p.18]]

3. System buses • In computer architecture, a bus is a transmission path that transfers data (actual data, address data or control data) between components inside a computer, or between computers. • Address bus carries address, data bus carries data and control bus carries control information.

4. Functions of Buses • 1. Data sharing - All types of buses found on a computer must be able to transfer data between the computer peripherals connected to it. • 2. Addressing - A bus has address lines, which match those of the processor. This allows data to be sent to or from specific memory locations. • 3. Power - A bus supplies power to various peripherals that are connected to it. • 4. Timing - The bus provides a system clock signal to synchronize the peripherals attached to it with the rest of the system.

5. Expansion buses • Devices such as keyboards and mice are so common that their controller circuitry and connectors are built right into the motherboard.  Even audio, video and LAN capabilities - at one time considered "specialized" devices - are now built into most motherboards.  Such motherboards are designed for their simplicity, and will usually decrease the cost of the overall PC.  However, it makes the system more expensive to repair, since a faulty component will usually require the entire motherboard to be replaced. However, integrated motherboards are not always suited for specialized applications.  For example, the data transfer rate for integrated video (133 MB/s) may not be enough for games or high-end graphics applications.  In addition, you may want to connect a specialized device that does not have a suitable port or connector on the motherboard.  For these devices, the controller circuitry and connectors are built into special circuit boards called expansion cards (or controller cards, or adapter cards), which are physically inserted into special “expansion slots” on the motherboard.

6. Expansion buses • The narrow channel in each expansion slot contains tiny copper contacts, which are connected to expansion buses.  When an expansion card is inserted into the expansion slot, a connection is made between the contacts in the slot and the copper “fingers” on the expansion card.  This allows the expansion card to use the associated expansion bus to communicate with an appropriate support chip, which ultimately allows the  device to communicate with the CPU.

7. Expansion buses

8. Some Expansion bus types • Expansion Bus Types: These are some of the common expansion bus types that have ever been used in computers: • PCI - Peripheral Component Interconnect • PCMCIA - Personal Computer Memory Card Industry Association (Also called PC bus) • AGP - Accelerated Graphics Port • SCSI - Small Computer Systems Interface

9. Expansion bus types • Peripheral Component Interconnect (PCI): It is one of the latest developments in bus architecture and is the current standard for expansion cards. It connects the CPU, memory and peripherals to wider, faster data pathway. • PCI supports both 32-bit and 64-bit data width; therefore it is compatible with 486s and Pentiums.

10. Expansion bus types • AGP: The need for high quality and very fast performance of video on computers led to the development of the Accelerated Graphics Port (AGP). The AGP Port is connected to the CPU and operates at the speed of the processor bus. This means that video information can be sent more quickly to the card for processing. The AGP uses the main PC memory to hold 3D images. In effect, this gives the AGP video card an unlimited amount of video memory. 

11. Expansion bus types • PC card: The Personal Computer Memory Card Industry Association was founded to provide a standard bus for laptop computers. So it is basically used in the small computers. • SCSI: Short for Small Computer System Interface, a parallel interface standard used by Apple Macintosh computers, PC's and Unix systems for attaching peripheral devices to a computer.

12. Expansion bus types • USB : This is an external bus standard that supports data transfer rates of 12 Mbps. A single USB port can be used to connect peripheral devices, such as mice, modems, and keyboards. The USB also supports hot plugging/insertion (ability to connect a device without turning the PC of) and plug and play (You connect a device and start using it without configuration).