What is USB and its TYPES.
USB full form is Universal Serial Bus.
Universal Serial Bus came into life when a group of 7 companies : Compaq, Digital Equipment, IBM, Intel, Microsoft and Northern Telecom decides to form a specifications to merge legacy connectivity such as RS232, Printer port, PS2 port into a single common connector to the Personal Computer.
Universal Serial Bus came into life when a group of 7 companies : Compaq, Digital Equipment, IBM, Intel, Microsoft and Northern Telecom decides to form a specifications to merge legacy connectivity such as RS232, Printer port, PS2 port into a single common connector to the Personal Computer.
Version 1.0
Version 1.0 of the USB specifications
delivered on 15 January 1996. Version 1.0 specifies 2 forms of signaling
transfer rate :
1.Low Speed (1.5Mbits/sec)
2. Full Speed (12Mbits/sec).
The
motivation of differentiating two transfer speed was to maintain the low-cost
implementation of computer peripherals such as keyboards and mice, and, still
allow higher speeds devices such that printers and scanners to be able to use
the same serial bus. The physical layer were layered with the protocol layer.
The protocol layer divides the bus time into several priorities of Control,
Interrupt, Bulk and Isochronous transfer. This protocol is handled through a
combination of hardware and software on the Personal Computer. The hardware
will be the USB Host Controller and the software will certainly be Microsoft's
Windows 95 OSR2.1 (at that time).
Like any technology, the start was slow and painful. The interaction of the software and USB Host Controller was specified into the Intel's Universal Host Controller Protocol or the Open Host Controller Protocol that was adopted by other vendors : Lucent, VIA... So, different base driver for OHCI and UHCI has to be developed on the Microsoft 95 OSR2.1 platform .
USB device's implementation has some timing that varies from one vendor to the other. The device driver to work on the PC was also changing from one bug fix to another. Having all these different variants of components working together was a difficult task.
The USB Implementor's Forum (USB-IF) then held Compliance workshop (Plugfest) quarterly to ensure that all the USB peripherals can work together. A 70% or more passing grade was given to those who can show enumeration and demonstrate workability. This margin has been upped to almost 95% today (2002).
Version USB1.1
Version 1.1 was delivered on 23 September 1998.
The 1.1 specifications clarified many timing parameters which were grey-areas
in the past. However, no huge "functional" improvements were given.
The success of USB was so-so during 1996 through 1997 as product vendors tries to maintain legacy compatibility. For instance, the addition of USB ports does not mean that the PS2, RS232 or the printer ports can be removed from the motherboard. This means that the cost the product is increased to accommodate legacy and still go with USB.
The turning point came with the introduction of the iMac computer. It showed an aesthetic system that consumers liked. More importantly, iMac provides the seeds that prompted vendors to manufacture USB peripherals.
Microsoft's introduction of the Windows 98 came at the right time as it provided the built-in USB drivers and the stability required to make USB fly.
Consumer who were using USB soon came to realize that although USB offers true plug and play feature, the bandwidth was significantly reduced if they were to concurrently run it with many USB devices. Or, a USB printer was not as fast as a parallel port printer.
In 27 April 2000, Compaq, Hewlett-Packard, Intel, Lucent, Microsoft, NEC and Philips released version 2.0 of the USB Specifications. While it adds a High Speed physical layer of (480 Mbits/sec), the specifications maintains the Low Speed and Full Speed operation. In effect was a handshake protocol was implemented to negotiate into the different speeds, a new High Speed Hub to manage all 3 speeds and a new Enhanced Host Controller to managed the faster bus and new PIDs to efficiently handle USB bandwidth.
The success of USB was so-so during 1996 through 1997 as product vendors tries to maintain legacy compatibility. For instance, the addition of USB ports does not mean that the PS2, RS232 or the printer ports can be removed from the motherboard. This means that the cost the product is increased to accommodate legacy and still go with USB.
The turning point came with the introduction of the iMac computer. It showed an aesthetic system that consumers liked. More importantly, iMac provides the seeds that prompted vendors to manufacture USB peripherals.
Microsoft's introduction of the Windows 98 came at the right time as it provided the built-in USB drivers and the stability required to make USB fly.
Consumer who were using USB soon came to realize that although USB offers true plug and play feature, the bandwidth was significantly reduced if they were to concurrently run it with many USB devices. Or, a USB printer was not as fast as a parallel port printer.
In 27 April 2000, Compaq, Hewlett-Packard, Intel, Lucent, Microsoft, NEC and Philips released version 2.0 of the USB Specifications. While it adds a High Speed physical layer of (480 Mbits/sec), the specifications maintains the Low Speed and Full Speed operation. In effect was a handshake protocol was implemented to negotiate into the different speeds, a new High Speed Hub to manage all 3 speeds and a new Enhanced Host Controller to managed the faster bus and new PIDs to efficiently handle USB bandwidth.
Note by simple:
USB 2.0 and USB 3.0 mentions
the speed of usb ports usb3.0 can transfer data faster than usb2.0 and their are some types of usb according to
their size and shape as mini usb,micro usb and standard usb.micro and mini usb mainly used for mobiles and
pda.