Question

Outline any four common bus standards that are used to provide parallel communication in embedded systems [3 marks each]

Embedded Systems

Answer 1

Industry Standard Architecture:

It is a 16-bit internal bus of IBM PC/AT and similar computers based on Intel 80286.I was created in 1981. The width in bits are 8 or 16.No of devices that can connect are upto 6. Speed is 8Mbps. It is a parallel bus. There was no hotplugging interface or external interface. It is still used for specialized industrial purposes. It is marketed to industrial and military users. Now-a-days, modern computers don't have physical ISA buses, all IBM compatible computers have ISA buses allocated in physical address space. Embedded systems and CPU's provide services such as temperature monitoring and voltage reading through these buses as ISA devices.

Front-side bus:

It is a computer communication interface bus that was often used in intel-chip based computers during 1990s and 2000s. Depending on implementations some computers even have back side buses which connects to cache. This bus and cache connected are faster than accessing the system memory via front-side. The speed of front side is often used as measuring the performance of computers.

Parallel ATA:

It is an interface standard for connection of storage devices such as hard disk, floppy disk etc. It uses underlying AT attachment and AT attachment packet interface standards. It is an internal storage device connector. It is designed by western digital and Compaq in 1986. Superseded by Serial ATA, did not have hot plugging or external interface. Cable used were 40 or 80 wires ribbon cable. There were total 40 pins and width was 16. Bitrate is 8.3Mbps maximum, later 33,66,100,133 Mbps were added. Maximum devices it can hold is 2 out of which one is master and another is slave. It uses Parallel protocol.

Conventional Peripheral Component Interconnect:

It is a local computer bus for attaching hardware devices in computer and is part of PCI local bus standard. Devices connected to PCI may appear to a bus master to be connected directly to its own bus and are connected directly to its own bus and are assigned addresses in the processor's address space. It Is a parallel bus and synchronous to a single bus clock. It was created on June 22,1992 by Intel. Width in bits are 32 or 64. Speed is 133Mbps on 32-bit at 33Mhz configurationor 266Mbpso 32-bit at 66-Mhz or 64-bits at 33Mhz or 533Mbps at 64-bits at 66-Mhz. Hotplugging is optional here. Attached devices can either take form of an integrated circuits fitted on motherboard or as an expansion card that fits into a slot. It has been adopted for other computer types.