同海才 TONGJI UNIV →1 ninput x2- Z2 m output variables variables Xn Zm Combinational circut y1 Y k secondary k excitation variables y2 Y variables (present (next state) state) yk Yk Delay Delay Delay 2002 Prentice Hall.Inc. M.Morris Mano Fig.9-1 Block Diagram of an Asynchronous Sequential Circuit DIGITAL DESIGN,3e
同桥大学 TONGJI UNIVERSITY How to analyze a asynchronous circuit? ● Check the feedback. o Do it in the combinational circuit way. ● Establish the state transition table
How to analyze a asynchronous circuit? ⚫Check the feedback. ⚫Do it in the combinational circuit way. ⚫Establish the state transition table
同海大学 TONGJI UNIVERSITY Fig.9-2 Example of an Asynchronous Sequential Circuit 2002 Prentice Hall.Inc. M.Morris Mano DIGITAL DESIGN,3e
同海大学 TONGJI UNIVERSITY 0 0 y1y2 y1y2 yiy2 00 0 0 00 0 00 00 01 1 0 01 1 1 01 11 01 11 1 1 11 0 11 11 10 10 0 10 0 0 10 00 10 (a)Map for (b)Map for (c)Transition table Y1=xy1+xy2 Y2=xy1+xy2 Fig.9-3 Maps and Transition Table for the Circuit of Fig.9-2 2002 Prentice Hall,Inc. M.Morris Mano DIGITAL DESIGN,3e
同桥大学 TONGJI UNIVERSITY Stable and unstable states The circle indicate the stable state. OUn-circled states are not stable,which means state transition could take place o The state transition will continue until the system reaches a stable state
Stable and unstable states ⚫The circle indicate the stable state. ⚫Un-circled states are not stable, which means state transition could take place ⚫The state transition will continue until the system reaches a stable state