Basic data transfer cycle that is used to pass only one chunk of data on every bus cycle. Read-modify-write Cycle An indivisible bus cycle that is used to pass semaphore information in multiprocessing systems. Multiplexed Block Transfer Cycles Similar to the BLT cycle, except that the address and data lines are combined to form wide address and data buses. Address-only cycle A type of cycle that only broadcasts an address. The VMEbus specification allows different address and data widths to be used based on an application requirement.
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Get this from a library! Boca Raton, Fla. Find more information about. Vmebus handbook PDF download. Peterson, VITA 1. For more details the user is directed to the handbook, or the VMEbus specification s. Introduction to VMEbus. VMEbus is a computer architecture. This group was composed of people from Motorola, Mostek and Signetics corporations who were cooperating to define the standard.
Q- bus. However, it is rarely used anymore. The microcomputer bus industry began with the advent of the microprocessor, and in 1. Most worked well with only one or two types of microprocessors, had a small addressing range and were rather slow. The VMEbus architects were charged with defining a new bus that would be microprocessor independent, easily upgraded from 1. No proprietary rights were assigned to the new bus, which helped stimulate third party product development.
Anyone can make VMEbus products without any royalty fees or licenses. In addition, a mechanical standard based on the Eurocard format was chosen. Eurocard is a term which loosely describes a family of products based around the DIN 4. IEC 6. PC board standards and the DIN 4. IEC 2. When VMEbus was first developed, the Eurocard format had been well established in Europe for several years.
A large body of mechanical hardware such as card cages, connectors and sub- racks were readily available. The pin and socket connector scheme is more resilient to mechanical wear than older printed circuit board edge connectors. It was released in 1. IEC 8. Since no proprietary rights are assigned to it, vendors and users need not worry that their products will become obsolete at the whim of any single manufacturer.
Since its introduction, VMEbus has generated thousands of products and attracted hundreds of manufacturers of boards, mechanical hardware, software and bus interface chips. It continues to grow and support diverse applications such as industrial controls, military, telecommunications, office automation and instrumentation systems.
There were several reasons why VMEbus was created in the first place. To understand these, we must first look back to the computer industry in about 1. These companies made big, bulky and expensive computers called mainframes and minicomputers. In the late 1. These were powered by small, low cost microprocessors that dramatically cut the size and price of the computer. They became immensely popular, and companies began to experiment with them in industrial control systems.
They found that desktop computers worked great in those applications, but had two major drawbacks.. Both were severe problems for the embedded control systems of the time. This was the situation in 1. VMEbus architecture was born. The new design combined the VERSAbus electrical specification, which was based on microprocessor technology, with the rugged and modular Eurocard packaging system. Both were proven, off- the- shelf technologies.
The resulting combination was successful because it solved the durability problem and could be easily adapted to a wide variety of applications.
However, this was only part of the story, as there was also a business strategy behind VMEbus that solved some very difficult market problems. By the time VMEbus arrived in 1. There were a variety of reasons for this, but a big one was the lack of technical standards.
For example, if you designed an accounting system around the IBM 3. IBM 3. This situation was very good for the computer companies of the day because it allowed each one to dominate a market niche. It was a sellers market where direct competition was squashed because there were few open technical standards. It was also bad for consumers i. They also had fewer choices because it was very difficult for third parties to enter the market with their own innovative ideas.
VMEbus was done a little differently. The original planners had the foresight to place the VMEbus specification into the public domain. This not only meant that everybody had to conform to the same technical standard, it also meant that they had to compete directly on the basis of price, performance, quality and time- to- market. It was a buyers market that meant lower margins for the suppliers, but also lower costs for the consumer i. The adoption of VMEbus as a public domain standard was a shrewd political move because it was easier to accept by a group of competitors.
The new market also had low barriers to entry which meant that third parties could enter the marketplace more easily. In the beginning, many predicted that this new, open marketplace was doomed to failure.
There were many sound business reasons for this at the time, but eventually it succeeded. Ironically, it was also good for the suppliers because the lower prices increased the demand for their products. They made lower margins, but made up for that with higher volumes. General VMEbus Features. These include but are not limited to mezzanine modules, crossbar switches, serial channels and high- availability type products.
Table 1. Asynchronous, with both multiplexed and non- multiplexed bus cycles. There is no central synchronization clock. Addressing Range. Address path width selected dynamically. Data Path Width. Data path width selected dynamically. Unaligned Data Transfers. Compatible with most popular microprocessors.
Error Detection. Parity Protection. There are no parity signals on the backplane, but parity protected boards are quite common. Data Transfer Rate.
See Table. Priority interrupt system with 8, 1. Multiprocessing Capability. Flexible bus arbitration with true peer- to- peer multiprocessing. System Diagnostic Capability. Geographical Addressing. Under VME6. Live Insertion Capability. Using optional standards. Mechanical Standard. U single- height Eurocard. U double- height Eurocard. U optional standard 1. Conduction Cooled Version Military Yes.
Under IEEE 1. Maximum Number of. Card Slots in Backplane. The number of cards is limited by how many boards, located on 0. VMEbus Applications. VMEbus is used in a wide variety of applications. In many cases, the VMEbus system design has been tailored to support specialized applications as well.
Some of the most popular include: Industrial controls: factory automation, robotics, injection molding machines, automotive body assembly and painting, sawmill controls, metal working, steel manufacturing, cardboard cutters and many others.
Aerospace: avionics, fly- by- wire control systems, in- flight video servers, spacecraft experiment control, missile countdown sequencers, and many others.
Wrong document context!
VMEbus User's Handbook