Timestamps –
Preserving Relative Transition Order
CE-653 - Hazards and Analysis
Methods
28
}maintaining the relative
order of transitions, based on finite gate delays, can be
achieved via timestamps
}Timestamp is a pair (i, t)
}i – signal group id – used
to indicate causal transitions
}t – time field – always
increments
}Timestamps are only kept
for signal transitions:
<0, ^, 1>, <1, v, 0> - not necessary for other values
<0, ^, 1>, <1, v, 0> - not necessary for other values
}Generating the i field for a multi-input gate (AND, OR)
}If output result stems
from input changes of same group (while other inputs remain
stable) è group id remains the
same
}Else if output result
stems from input changes of multiple groups è generate new group id
for the output signal and mark as successor
}Successor group ids indicated via group mask of signal
}bit per predecessor of current group id – 1 indicates true, 0
false
18/3/2014