MC74AC4040D

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MC74AC4040D is a 12-bit synchronous reversible up/down counters which includes an up/down control input and operates from a single positive power supply. The MC74AC4040D Synchronous Up/Down Counters utilize advanced Silicon–Gate CMOS technology for high speed and low power consumption. These counters are fully synchronous with a 3–input fast reset. The PE input sets the output to the low logic state regardless of the count.

The MC74AC4040D devices are readily applicable for counting and frequency division applications. The synchronous up/down counting simplify cascade connections between two counters and synchronization between data and clock. The two cascaded counters can be operated as an asynchronous up/down counter or as a modulo-N counter. The fast reset input greatly simplify reset signals received when the device is operated in parallel with other devices or requires reset of each count during normal operation.

The MC74AC4040D is also applicable to many other logic applications, such as dividers, decoders, shift registers, analogue switches and many other basic applications to real–world applications.

Working Principle

The MC74AC4040D counters incorporate a dual D–type flip flop for the counting logic with its own dedicated clock, which allows for a more efficient operation. The up/down control RX, allows for the up/down functionality at each clock pulse. The output from stage 1 is fed to stage 2 and so on, until it reaches the last stage – 12 in this case. This serves to increase the counting range allowing for higher overall count. When the PE (parallel enable) input is low, the outputs are forced to low, disregarding the other inputs.

The MC74AC4040D reversible synchronous up/down counters include an up/down control line Rx, carry and borrow lines Cx and Bx respectively, a reset line RESx, and a parallel enable line PE. The PE input line can be used to simultaneously set all counter outputs to either the low logic state (0) or the high logic state (1). When Rx input is low the circuit counts up, otherwise it counts down. The output of the last stage (stage 12 in this case) will toggle each time the count is completed in either direction and can be used as a clocking signal.

As the MC74AC4040D counters are synchronous, the clock lines are common to all the stages. One advantage of this is that the load on each stage is essentially determined by the previous stage, thus greatly improving propagation delay, as compared to asynchronous counter stages.

The MC74AC4040D counters are available in either the SE (standard) or the SI (low–power) packages. The SE package has a higher power dissipation rating than the SI package, and is thus recommended for applications with high fan–out requirements.

The MC74AC4040D also offer a fast synchronous reset, which can be used to reset the counters to its initial preset count, regardless of the states of the other inputs. This feature enables the use of the counters in high speed applications, such as clocks, frequency dividers and pulse width modulators, which require a quick and reliable reset signal.

Applications

The MC74AC4040D reversible synchronous up/down counters are ideal for both low– and high–frequency applications, such as digital clocks, frequency dividers and pulse–width modulators. The up/down control and asynchronous loading functions allow for simple cascaded connection between two counters, and synchronization between data and clock.

The MC74AC4040D is also suitable for other logic applications, such as dividers, decoders, and shift registers. The fast reset input greatly simplifies reset signals received when the device is operated in parallel with other devices or requires reset of each count during normal operation. The PE input allows simultaneous setting of the output states to either the low or high logic state.

Additionally, the MC74AC4040D counters have the ability to be operated in modulo 12 or modulo 9 modes, depending on the user-defined count range required. By using the Cx and Bx inputs, it is also possible to cascade two counters and program the output as either a modulo-N counter or as an asynchronous up/down counter.

The MC74AC4040D counters have very low power dissipation, making them particularly well-suited for battery–powered applications. The fast reset input also allows for very fast resetting of the counters, even under extreme temperatures.

The MC74AC4040D counters provide excellent performance characteristics and features such as fast synchronous reset and up/down count options. These features make the MC74AC4040D counters a highly desirable choice for a wide variety of applications, such as digital clocks, frequency dividers, and pulse–width modulators.

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