Critical race conditions often happen when the processes or threads depend on some shared state. Critical race conditions cause invalid execution and software bugs. Often logic redundancy can be added to eliminate some kinds of races.Īs well as these problems, some logic elements can enter metastable states, which create further problems for circuit designers.Ī race condition arises in software when a computer program, to operate properly, depends on the sequence or timing of the program's processes or threads. Sometimes they are cured using inductive delay line elements to effectively increase the time duration of an input signal.ĭesign techniques such as Karnaugh maps encourage designers to recognize and eliminate race conditions before they cause problems. It can be eliminated by using no more than two levels of gating.Īn essential race condition occurs when an input has two transitions in less than the total feedback propagation time. They are due to interaction between gates. Static, dynamic, and essential forms Ī static race condition occurs when a signal and its complement are combined.Ī dynamic race condition occurs when it results in multiple transitions when only one is intended. Critical and non-critical forms Ī critical race condition occurs when the order in which internal variables are changed determines the eventual state that the state machine will end up in.Ī non-critical race condition occurs when the order in which internal variables are changed does not determine the eventual state that the state machine will end up in. O u t p u t = A ∧ A ¯ changes from false to true then a brief period will ensue during which both inputs are true, and so the gate's output will also be true.
Certain systems can tolerate such glitches but if this output functions as a clock signal for further systems that contain memory, for example, the system can rapidly depart from its designed behaviour (in effect, the temporary glitch becomes a permanent glitch).Ĭonsider, for example, a two-input AND gate fed with the following logic:
The output may, for a brief period, change to an unwanted state before settling back to the designed state. The inputs to the gate can change at slightly different times in response to a change in the source signal.
0 kommentar(er)
