1. An 7-bit counter is wired as follows: The CLK input to the first stage (LSB) is the system clock. Each stage's output is used as the CLK input to the next higher stage. This counter is a:
A. MOD 128 ripple counter
B. MOD 256 synchronous counter
C. MOD 256 ripple counter
D. MOD 128 synchronous counter
2. Which group of logic devices represents the minimum hardware required for a MOD 128 synchronous counter?
A. four flip flops, two AND gates
B. five flip flops, three AND gates
C. six flip flops, four AND gates
D. seven flip flops, five AND gates
3.A 50 kHz clock pulse is applied to a MOD-20 ripple counter. What is the output frequency?
A. 1.88 kHz
B. 1.55 kHz
C. 2.5 kHz
D. 2kHz
4. A production plant needs a counter that will count 1,800 items before resetting and recycling. How many flip-flop stages would this counter require?
A. 13
B. 10
C. 11
D. 12
deded
1. The correct answer is D. MOD 128 synchronous counter. Since each stage's output is used as the CLK input to the next higher stage, this indicates synchronous behavior. And since there are 7 stages, the counter can count up to 2^7 = 128, making it a MOD 128 counter.
2. The correct answer is C. six flip flops, four AND gates. To create a MOD 128 synchronous counter, you need one flip flop for each binary digit in the MOD value (128), which is 7. Additionally, for each flip flop, you need one AND gate to combine the appropriate inputs. Therefore, you would need 7 flip flops and 3 AND gates, making the total hardware required six flip flops and four AND gates.
3. The output frequency of a ripple counter is equal to the input frequency divided by the MOD value. In this case, the input frequency is 50 kHz and the MOD value is 20. Therefore, the output frequency is 50 kHz / 20 = 2.5 kHz. So the correct answer is C. 2.5 kHz.
4. To determine the number of flip-flop stages required, you need to find the smallest power of 2 greater than or equal to 1,800. In this case, the smallest power of 2 that is greater than or equal to 1,800 is 2^11 = 2,048. Therefore, you would need 11 flip-flop stages to count up to 1,800 before resetting and recycling. So the correct answer is C. 11.
1. To determine the type of counter, we need to understand the characteristics of ripple counters and synchronous counters.
A ripple counter is a type of counter where the output of each stage serves as the clock input for the next stage. This means that the clock signal ripples through each stage, causing a delay between each stage's transition. The output frequency of a ripple counter is determined by the propagation delay between stages.
A synchronous counter, on the other hand, uses a common clock signal that is applied to all stages simultaneously. The outputs of all the stages change simultaneously on each clock pulse, eliminating the propagation delay between stages. The output frequency of a synchronous counter is the same as the clock frequency.
In this case, we are given that the CLK input to the first stage is the system clock, and each stage's output is used as the CLK input to the next stage. This arrangement suggests that the counter is a synchronous counter since all stages receive the clock signal simultaneously.
Now, we need to determine the MOD value of the counter. The MOD value represents the number of unique states the counter can reach before it repeats. To find the MOD value, we count the number of flip-flop stages in the counter.
The given counter is a 7-bit counter, which means it has 7 flip-flop stages. Therefore, the MOD value is 2^7 = 128.
From the above discussion, we can conclude that the counter is a MOD 128 synchronous counter. Hence, the answer is option D - MOD 128 synchronous counter.
2. To determine the minimum hardware required for a MOD 128 synchronous counter, we need to calculate the number of flip-flop stages and the number of AND gates needed.
The MOD value of the counter is 128, which means the counter needs to track and count up to 128 unique states before it repeats. To count up to 128, we need a binary counter with at least 7 bits since 2^7 = 128.
Each flip-flop stage represents a single bit in the binary counter. Therefore, the number of flip-flop stages needed is 7.
In a synchronous counter, the clock signal is applied to all stages simultaneously. So, we don't need any additional AND gates for clock inputs.
Hence, the minimum hardware required for a MOD 128 synchronous counter is 7 flip-flops.
Therefore, the answer is option D - seven flip flops, five AND gates.
3. To calculate the output frequency of a MOD-20 ripple counter when a 50 kHz clock pulse is applied, we need to understand how the MOD value affects the output frequency.
The MOD value represents the number of unique states the counter can reach before it repeats. In this case, the counter is a MOD-20 ripple counter, so it can count up to 20 unique states before it repeats.
To calculate the output frequency, we need to divide the input clock frequency by the MOD value.
Output frequency = Input clock frequency / MOD value
Output frequency = 50 kHz / 20
Output frequency = 2.5 kHz
Therefore, the output frequency of the MOD-20 ripple counter is 2.5 kHz. Hence, the answer is option C - 2.5 kHz.
4. To determine the number of flip-flop stages required for a counter that counts 1,800 items before resetting and recycling, we need to determine the MOD value of the counter.
The MOD value represents the number of unique states the counter can reach before it repeats. In this case, the counter needs to count up to 1,800 items before resetting, which means the MOD value is 1,800.
To calculate the number of flip-flop stages, we need to find the minimum number of bits required to represent the MOD value. The number of bits can be calculated using the formula:
Number of bits = ceil(log2(MOD value))
Using this formula:
Number of bits = ceil(log2(1800))
Number of bits = ceil(10.813)
Number of bits = 11
Therefore, the counter would require 11 flip-flop stages. Hence, the answer is option C - 11 flip-flop stages.