效绵 Discrete Time Domain choose a fixed sample period s all events happen at multiples of s simple extension of classical models main disadvantage -how to choose s bige→too coarse model o low 8=>time fragmentation,too big state space usage:particularly synchronous systems (hardware circuits)Discrete Time Domain ◼ choose a fixed sample period ε ◼ all events happen at multiples of ε ◼ simple extension of classical models ◼ main disadvantage — how to choose ε ?  big ε  too coarse model  low ε  time fragmentation, too big state space ◼ usage: particularly synchronous systems (hardware circuits)