Practice Question

Duration: 2 min

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The video features an educational lecture solving a specific digital logic problem involving a 32-bit shift register. The problem statement displayed on the screen asks for the total time required to perform loading and reading operations when the register operates in SISO (Serial In Serial Out) mode with a clock frequency of 1 GHz. The available options are 1 ns, 31 ns, 32 ns, and 63 ns. The instructor systematically breaks down the question by underlining critical terms such as "32-bit shift register," "1 GHz," "SISO mode," and the specific task of "loading and reading." He identifies the number of bits, n, as 32 and the frequency, f, as 1 GHz. To solve this, he writes on the whiteboard, illustrating the concept of Serial Input (SI) and Serial Output (SO). He introduces the formula for the total number of clock cycles required in a SISO configuration, which is 2n - 1. He substitutes the value of n=32 into this equation, calculating 2(32) - 1, which results in 63 clock cycles. Next, he determines the time period of a single clock cycle using the formula T = 1/f. With f = 1 GHz (1 x 10^9 Hz), the time period T is calculated as 1 nanosecond (1 ns). Finally, he multiplies the total number of clock cycles (63) by the time period per cycle (1 ns) to find the total time, resulting in 63 ns. He concludes by circling the calculated answer and selecting option (d) from the multiple-choice list provided.

Chapters

  1. 0:00 1:36 00:00-01:36

    The instructor presents a problem about a 32-bit shift register with a 1 GHz clock in SISO mode. He underlines key terms, writes the formula 2n-1 on the board, calculates 63 clock cycles, determines the clock period is 1 ns, and multiplies them to find the total time of 63 ns.

The lecture demonstrates a standard approach to timing analysis in digital circuits. By identifying the mode of operation (SISO), the instructor applies the specific formula for clock cycles (2n-1) rather than just n. This highlights the distinction between loading and reading times in serial operations, where data must be shifted in and then shifted out. The calculation of the clock period from frequency is a fundamental step, linking the abstract clock signal to physical time. The final multiplication combines these two values to provide the total duration, reinforcing the relationship between frequency, cycles, and time in sequential logic design. This method is crucial for understanding latency in shift register applications.