That is, the delay stage sets the amount of time that the transparent latch is open, and for most purposes, it's an infinitesimal period of time that roughly corresponds to just the edge of the clock pulse.
22.
Since they don't have to wait for a clock pulse to begin processing inputs, asynchronous circuits can be faster than synchronous circuits, and their speed is theoretically limited only by the propagation delays of the logic gates.
23.
The interval between clock pulses must be long enough so that all the logic gates have time to respond to the changes and their outputs " settle " to stable logic values, before the next clock pulse occurs.
24.
For example, if one clock pulse latches a value into a register or begins a calculation, it will take some time for the value to be stable at the outputs of the register or for the calculation to complete.
25.
When the clock pulse occurs, the sum will be transferred to storage and, if the resulting sum is too large ( i . e ., it is larger than the ALU's output word size ), an arithmetic overflow flag will be set.
26.
Input information applied at D is transferred to Q on the occurrence of the positive edge of the clock pulse . thus when the comparator output ( e ) is positive Q goes positive or remains positive at the next positive clock edge.
27.
However, when I set the second set of flip flops, the set causes pin Q to be taken high in relevent flip flops, which is counted as a clock pulse by the next flip flop in the counting set, causing unwanted bit generaton.
28.
In this example the fine measurement circuit measures the time between start and stop pulse and the respective second nearest clock pulse of the coarse counter ( " T " start, " T " stop ), detected by the synchronizer ( see figure ).
29.
The metastability in flip-flops can be avoided by ensuring that the data and control inputs are held valid and constant for specified periods before and after the clock pulse, called the "'setup time "'( t su ) and the "'hold time "'( t h ) respectively.
30.
One may consider this clock pulse redundant information, or at least a wasteful use of channel capacity, and duplex the channel by varying the phase, as in polar modulation, or adding another signal that is 90?out of phase ( a sine wave ), as in quadrature modulation.
