A counter circuit is usually constructed from a number of flip-flops connected in the cascade. Counters are components that are widely used in digital circuits, and are manufactured as separate integrated circuits and also incorporated as part of larger integrated circuits.
Video Counter (digital)
Electronic counter
In electronics, counters can be implemented easily using register-type circuits such as flip-flops, and assorted are classified into:
- Asynchronous counters (ripple) - change state bit used as clock to next state flip-flop
- Sync counters - all status bits change under one hour control
- Decade of counting - calculated through ten countries per stage
- Counters rise/fall - count both up and down, under control input command
- Ring counter - formed by shift register with feedback connection in loop
- The Johnson counter - the ring counter plays
- Counters multilevel
- The modulus counter.
Each is useful for different applications. Typically, the counter circuit is digital, and is calculated in a natural binary. Many types of counter circuits are available as digital building blocks, for example a number of chips in the 4500 series apply different counters.
Sometimes there is the advantage of using a count sequence other than a natural binary sequence - such as a binary coded decimal counter, linear feedback shift register, or a Gray code counter.
Counters are useful for digital clocks and timers, and oven timers, VCR clocks, etc.
Asynchronous (ripple) counter
Asynchronous counter (ripple) is a single-d flip-flop type, with input J (data) fed from its own invert output. This circuit can store one bit, and therefore can be counted from zero to one before overflow (starting from 0). This count will increase once for every clock cycle and it takes two clock cycles to overflow, so each cycle will alternate between the transition from 0 to 1 and the transition from 1 to 0. Note that this creates a new clock with 50% duty cycle exactly on half the frequency of the input clock. If this output is then used as a clock signal for the same regulated D-flop (remembering to reverse the output to the input), someone will get another 1 bit counter that counts half quickly. Putting them together produces a two-bit counter:
You can continue to add additional flip flops, always reverse the output to its own input, and use the output of the previous flip-flop as the clock signal. The result is called a counter ripple, which can be calculated up to 2 n - 1 where n is the number of bits (flip stage -flop) at the counter. Ripple counters suffer from unstable output as a "ripple" overflow from stage to stage, but they find frequently used applications as dividers for clock signals, where instantaneous counts are not important, but the overall division ratio is (to clarify this, 1- the bit counter is exactly equal to divide by two circuits, the output frequency is exactly half of the input when fed with regular train clock pulses).
The use of the flip-flop output as a clock causes a sloping time between bits of data, making this ripple technique incompatible with the normal synchronous circuit design style.
Sync counter
In the sync counter, the clock input of all the flip-flops is connected together and triggered by the input pulse. Thus, all the flip-flop changes simultaneously (in parallel). The circuit below is a 4-bit sync counter. The J and K inputs of FF0 are connected to HIGH. FF1 has J and K inputs connected to the FF0 output, and the J and K inputs of FF2 are connected to the output of the AND gate fed by the FF0 and FF1 outputs. A simple way to implement logic for each bit of the risers (depicted in adjacent images) is for each bit to switch when all the less significant bits are in logic high state. For example, bit 1 turns off when bit 0 is logic high; bit 2 turn off when bit 1 and bit 0 are logic high; bit 3 turn off when bit 2, bit 1 and bit 0 are all high; etc.
Sync counters can also be implemented with finite state hardware machines, which are more complex but allow for smoother and more stable transitions.
Decade Decade
A decade counter is a count that is counted in decimal digits, not binaries. Counters of a decade can have each (that is, this can be counted in binary-coded decimal, as do 7490 integrated circuits) or other binary encodings. "Decade counters are binary counters designed to count up to 1010 (decimal 10).A usual four-stage counter can be easily modified to decade counters by adding NAND gates as in the schematic to the right.Note that FF2 and FF4 provide input to NAND gates. the NAND gate is connected to the CLR input of each FF. "A decade counter is a count that is counted in decimal digits, not binaries. This is calculated from 0 to 9 and then reset to zero. The output counter can be set to zero by vibrating a low reset line. The count then increases on every clock pulse until it reaches 1001 (decimal 9). When the addition to 1010 (decimal 10) both inputs from the NAND gate becomes high. The result is a low NAND output, and resets the counter to zero. D can be a CARRY OUT signal, indicating that there is a count of ten.
Ring counter
The ring counter is a circular shift register which is initiated in such a way that only one of its flip-flops is a state while the other is in zero state.
The ring counter is a shift register (cascade connection of flip-flops) with output from the latter connected to the first input, that is, in a ring. Typically, a pattern consisting of a single bit is passed so that the state repeats every clock cycle n if n flip-flop is used.
Johnson Counter
The Johnson counter (or tail-ring ring counter, circular ring counter, running ring counter, or MÃÆ'¶bius counter) is a modified ring counter, where the output of the last stage is reversed and re-entered as input to the first stage. The register cycles through a bit-pattern sequence, which is equal to twice the length of the shift register, continuing indefinitely. These counters find custom apps, including similar ones to decade counters, digital-to-analog conversion, etc. They can be implemented easily using D- or JK-type flip-flops in this counting process
Maps Counter (digital)
Computer science counter
In computability theory, a counter is considered a memory type. A counter keeps a single natural number (originally zero) and can be arbitrarily long. Counters are usually considered along with state-limited machines (FSM), which can perform the following operations on the counter:
- Check if the counter is zero
- Increase the counters after another.
- Lowering the counter one by one (if it is zero, this does not change).
The following machines are listed in order of strength, with each machine strictly stronger than the one below them:
- Deterministic or non-deterministic FSM plus two counters
- Non-deterministic FSM plus one stack
- Non-deterministic FSM plus one counter
- Deterministic FSM plus one counter
- Deterministic or non-deterministic FSM.
For the first and last, it does not matter whether FSM is a finite deterministic automaton or an infinite unlimited automat. They have the same power. The first two and the last are the levels of Chomsky's hierarchy.
The first machine, FSM plus two counters, is equivalent to a Turing machine. See the article on enumerator for evidence.
Web counter
The web or hit count counterpart is a computer software program that shows the number of visitors, or clicks, a specific web page has been received. Once set, this counter will increment one each time a web page is accessed in a web browser.
This number is usually shown as an inline digital image or in plain text or on a physical counter such as a mechanical counter. Images can be presented in various fonts, or styles; the classic example is the odometer wheel.
Web counter was popular in the mid to late 1990s and early 2000s, then replaced by more detailed and complete web traffic measures.
Computer based counters
Many automation systems use PCs and laptops to monitor various machine parameters and production data. The counter can calculate parameters such as number of pieces produced, batch production number, and measurement of the amount of material used.
Mechanical counters
Long before electronics became common, mechanical devices were used to calculate events. This is known as a counting counter. They usually consist of a series of disks mounted on the axis, with numbers zero to nine marked at the end. The rightmost disc moves one difference with each event. Every disk except the far left has a bulge that, after the completion of a revolution, moves the next disk to one remaining margin. Such counters are used as odometers for bicycles and cars and in tape recorders, fuel dispensers, in production machines and also in other machines. One of the largest manufacturers is the Veeder-Root company, and their name is often used for this type of counter.
Counter counters are used primarily for inventory and for counting people attending events.
Electromechanical counters are used to collect the total in a tabulation machine that pioneered the data processing industry.
See also
- Time for digital converter
- Geneva drive
- Speed ​​count beads
- Prayer
References
External links
- Media associated with the Counter circuit on Wikimedia Commons
Source of the article : Wikipedia
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