Master slave flip flop vs edge triggered flip flop

Master slave flip flop vs edge triggered flip flop mod#

To make a MOD-10 counter, you simply start with the MOD-16 counter and connect the Q0 and Q3 outputs to a NAND gate, as shown in the figure.When the counter reaches 9 (1001), Q 0 and Q3 will both go high, causing the NAND gateвЂ™s output to go low. The figure below shows just such a circuit.

Likewise, what do you do if you want to stop the counter after a particular count has been reached and then trigger some device, such as an LED or buzzer.

Master slave flip flop vs edge triggered flip flop mod#

But how do you create a ripple counter with a MOD value other than 2, 4, 8, 16, etc.? For example, say you want to create a MOD-10 (0 to 9) ripple counter. Ripple counters with higher MOD values can be constructed by slapping on more flip-flops to the MOD-16 counter. To get a divide-by-2 counter, you only need the first flip-flop to get a divide-by-8 counter, you need the first three flip-flops. Here, you simply replace the clock signal with any desired input signal that you wish to divide in frequency. The ripple counter above also can be used as a divide-by-2,4,8,16 counter. To reset the counter at any given time, the active-low clear line is pulsed low.To make the counter count backward from 1111 to 0000, you would simply use the QвЂ™ outputs. When the count reaches 1111, the counter recycles back to 0000 and continues from there. The least significant bit (LSB) is Q0, while the most significant bit (MSB) is Q4. What you get in the end is a binary counter with four digits. The second flip-flop receives Q0вЂ™s output at its clock input and likewise divides by 2. The clock signal applied to the first flip-flop causes the flip-flop to divide the clock signalвЂ™s frequency by 2 at its Q0 output-a result of the toggle. Each flip-flop in the ripple counter is fixed in toggle mode (J and K are both held high). (MOD-16, or modulus 16, means that the counter has 16 binary states.) This means that it can count from 0 to 15- the zero is one of the counts. Ripple Counter (Asynchronous Counter) :ДЄsimple counter, called a MOD-16 ripple counter (or asynchronous counter), can be constructed by joining four JK flop-flops together, as shown in Fig. The truth table and timing diagram below help illustrate how this device works.Дў. When the clock is low, the inputs are disabled, and the flip-flop is placed in hold mode.

To make the preceding SR flip-flop into a synchronous or clocked device, simply attach enable gates to the inputs of the flip-flop, as shown in Fig.(Here, the cross-NAND arrangement is used, though a cross-NOR arrangement also can be used.) Only when the clock is high are the S and R inputs enabled. Flip-flops that respond in this manner are referred to as synchronous or clocked flip-flops (as opposed to the preceding asynchronous flip-flops). Only when the clock pulse arrives are the inputs sampled. Now it would be nice to make an SR flip-flop synchronous-meaning making the S and R inputs either enabled or disabled by a control pulse, such as a clock. As you will see later when I discuss flip-flop applications, the ability to apply asynchronous set and resets is often used to clear entire registers that consist of an array of flip-flops. These active-low inputs are therefore normally pulled high to make them inactive. When C_L_R_ is high and P_R_E_ is low, you get asynchronous reset, Q = 1, QвЂ™ = 0, regardless of the CLK, S, and R inputs. Unlike the synchronous inputs, S and R, the asynchronous input disregard the clock and either clear (also called asynchronous reset) or preset (also called asynchronous set) the flip-flop. Notice the preset (P_R_E_) and clear (C_L_R_) inputs. The moment the slave is enabled, it uses the Y and YвЂ™ outputs of the master as inputs and then outputs the final result.

The slave is similar to the master, but it gets enabled only during the negative clock pulse (due to the inverter). Another analogy often used is to say that during the positive edge, the master gets cocked (like a gun), and during the negative clock edge, the slave gets triggered.The master is simply a clocked SRДЇlip-flop that is enabled during the high clock pulse and outputs Y and Y_ (either set, reset, or no change). Pulse-triggered flip-flops are also called master-slave flip-flop the master accepts the initial inputs and the вЂњwhipsвЂќ the slave with its output when the negative clock edge arrives. A pulse-triggered SR flip-flop is a level-clocked flip-flop however, for any change in output to occur, both the high and low levels of the clock must rise and fall.