17-07-2012, 04:02 PM
Design and implementation of Elevator Controller using VHDL
Design and implementation of Elevator Controller using VHDL.doc (Size: 580 KB / Downloads: 157)
The high growth of the semiconductor industry over the past two decades has put Very Large Scale Integration in demand all over the world. The basics of digital logic theory and techniques are easily understood by the design based on VLSI technology. These are the core fundamentals of the fast, high-speed complex digital circuits.
In modern life, elevators have become an integral part of any public or commercial complex. It does not only ease the faster movement between any two floors and provide a way for movement of disabled, but has also become a status symbol. Elevators, as usually been called as “cars” which work on a gearless traction system in which the movement of the elevator is controlled by several steel hoist ropes and a counter-weight. The weight of the car and counterweight provides sufficient traction between the sheaves and the hoist ropes so that the sheaves can grip the hoist ropes and move and hold the car without excessive slipping. The machinery to drive the elevator is located in a machine room usually directly above the elevator hoist way. To feed electricity to the car and receive electrical signals from it, a multi-wire electrical cable connects the machine room to the car.
Elevator controller controls the entire operation of the elevator system. In this work, the real-time elevator controller will be modeled with VHDL code using Finite-State machine (FSM) model to achieve the logic in optimized way. This projects shows how the elevator can control the movement of elevator from up to down and vise versa and how it limits the no of persons through controller.
1. VLSI
1.1. INTRODUCTION
Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistor-based circuits into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device. The term is no longer as common as it once was, as chips have increased in complexity into the hundreds of millions of transistors.
Overview
The first semiconductor chips held one transistor each. Subsequent advances added more and more transistors, and, as a consequence, more individual functions or systems were integrated over time. The first integrated circuits held only a few devices, perhaps as many as ten diodes, transistors, resistors and capacitors, making it possible to fabricate one or more logic gates on a single device. Now known retrospectively as "small-scale integration" (SSI), improvements in technique led to devices with hundreds of logic gates, known as large-scale integration (LSI), i.e. systems with at least a thousand logic gates. Current technology has moved far past this mark and today's microprocessors have many millions of gates and hundreds of millions of individual transistors.
At one time, there was an effort to name and calibrate various levels of large-scale integration above VLSI. Terms like Ultra-large-scale Integration (ULSI) were used. But the huge number of gates and transistors available on common devices has rendered such fine distinctions moot. Terms suggesting greater than VLSI levels of integration are no longer in widespread use. Even VLSI is now somewhat quaint, given the common assumption that all microprocessors are VLSI or better.
As of early 2008, billion-transistor processors are commercially available, an example of which is Intel's Montecito Itanium chip. This is expected to become more commonplace as semiconductor fabrication moves from the current generation of 65 nm processes to the next 45 nm generations (while experiencing new challenges such as increased variation across process corners). Another notable example is NVIDIA’s 280 series GPU.
This microprocessor is unique in the fact that its 1.4 Billion transistor count, capable of a teraflop of performance, is almost entirely dedicated to logic (Itanium's transistor count is largely due to the 24MB L3 cache). Current designs, as opposed to the earliest devices, use extensive design automation and automated logic synthesis to lay out the transistors, enabling higher levels of complexity in the resulting logic functionality. Certain high-performance logic blocks like the SRAM cell, however, are still designed by hand to ensure the highest efficiency (sometimes by bending or breaking established design rules to obtain the last bit of performance by trading stability).
What is VLSI?
VLSI stands for "Very Large Scale Integration". This is the field which involves packing more and more logic devices into smaller and smaller areas.
Simply we say Integrated circuit is many transistors on one chip.
Design/manufacturing of extremely small, complex circuitry using modified semiconductor material
Integrated circuit (IC) may contain millions of transistors, each a few mm in size
Applications wide ranging: most electronic logic devices
1.2. History of Scale Integration
late 1940s Transistor invented at Bell Labs
late 1950s First IC (JK-FF by Jack Kilby at TI)
early 1960s Small Scale Integration (SSI)
10s of transistors on a chip
late 1960s Medium Scale Integration (MSI)
100s of transistors on a chip
early 1970s Large Scale Integration (LSI)
1000s of transistor on a chip
early 1980s VLSI 10,000s of transistors on a
chip (later 100,000s & now 1,000,000s)
Ultra LSI is sometimes used for 1,000,000s
SSI - Small-Scale Integration (0-102)
MSI - Medium-Scale Integration (102-103)
LSI - Large-Scale Integration (103-105)
VLSI - Very Large-Scale Integration (105-107)
ULSI - Ultra Large-Scale Integration (>=107)
1.3. Advantages of ICs over discrete components
While we will concentrate on integrated circuits , the properties of integrated circuits-what we can and cannot efficiently put in an integrated circuit-largely determine the architecture of the entire system. Integrated circuits improve system characteristics in several critical ways. ICs have three key advantages over digital circuits built from discrete components:
Size. Integrated circuits are much smaller-both transistors and wires are shrunk to micrometer sizes, compared to the millimeter or centimeter scales of discrete components. Small size leads to advantages in speed and power consumption, since smaller components have smaller parasitic resistances, capacitances, and inductances.
Speed. Signals can be switched between logic 0 and logic 1 much quicker within a chip than they can between chips. Communication within a chip can occur hundreds of times faster than communication between chips on a printed circuit board. The high speed of circuits on-chip is due to their small size-smaller components and wires have smaller parasitic capacitances to slow down the signal.
Power consumption. Logic operations within a chip also take much less power. Once again, lower power consumption is largely due to the small size of circuits on the chip-smaller parasitic capacitances and resistances require less power to drive them.
VLSI and systems
These advantages of integrated circuits translate into advantages at the system level:
Smaller physical size. Smallness is often an advantage in itself-consider portable televisions or handheld cellular telephones.
Lower power consumption. Replacing a handful of standard parts with a single chip reduces total power consumption. Reducing power consumption has a ripple effect on the rest of the system: a smaller, cheaper power supply can be used; since less power consumption means less heat, a fan may no longer be necessary; a simpler cabinet with less shielding for electromagnetic shielding may be feasible, too.
Reduced cost. Reducing the number of components, the power supply requirements, cabinet costs, and so on, will inevitably reduce system cost. The ripple effect of integration is such that the cost of a system built from custom ICs can be less, even though the individual ICs cost more than the standard parts they replace.
Understanding why integrated circuit technology has such profound influence on the design of digital systems requires understanding both the technology of IC manufacturing and the economics of ICs and digital systems.
Applications
Electronic system in cars.
Digital electronics control VCRs
Transaction processing system, ATM
Personal computers and Workstations
Medical electronic systems.