SN74HC191NSR

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The SN74HC191NSR is a 4-bit synchronous binary up/down counter. It is a high-speed, low-power device that combines synchronous counter operations with look-ahead count functions. This device has two independent synchronous 4-bit counters with both count up and count down capabilities. The synchronous counter operations are controlled with a count enable (CE) input. All synchronous inputs and outputs are latched on the rising edge of the clock (CLK). The device also has a carry look-ahead capability for fast cascading operation. Additionally, the device has Terminal Count (TC) outputs for each counter which indicates when the counter has reached terminal count (0000 or 1111).

The SN74HC191NSR is a good choice in applications where extremely low power consumption is prevalent, such as clock oscillators, system clocks, and general-purpose counters. In clock oscillators and system clocks, the SN74HC191NSR can be used to perform a programmable count-up and count-down function. When used as a general-purpose counter, the SN74HC191NSR can be used in digital multiplexer systems, low-power modulus counters, parallel data processing systems, bus counting, and many other applications. The device can also be used in high-speed pulse generators and divide-by-N counters.

The working principle of the SN74HC191NSR is based on a 4-bit synchronous counter with both count-up and count-down capability. The counter has a count control input, Count Enable (CE), which controls the counting operation. When CE is set high, the counter will count in the directions determined by the Up/Down Control bit (U/D). The count starts from 0000 and will either keep counting at each clock pulse or stop at TC (Terminal Count) when the count reaches 1111 for up count or 0000 for down count. The TC signals are fed back to the U/D pin to control the counter’s direction. When TC is high, the count direction of the SN74HC191NSR is set to down count, and the count will continue until the count reaches 0000. When TC is low, the count direction of the SN74HC191NSR is set to up count and the count will continue until the count reaches 1111. The IC also has an asynchronous clear signal that can be used to reset the counter.

In summary, the SN74HC191NSR is an ideal IC for applications where low power is needed, or for use in systems that require synchronization. The device provides a synchronous 4-bit counter for both count-up and count-down operations. The Counter has a TC Output for each counter which indicates when the counter has reached its terminal count (0000 or 1111). Having this capability allows for the use of cascading multiple SN74HC191NSRs, allowing the build up of larger counters with minimal control logic. The static design of the device also minimizes power consumption, making it ideal for applications where energy efficiency is paramount.

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