Control method and device for approximate adder circuit based on memristor

A control method for an approximate adder circuit based on memristor, for implementing an approximate addition of n-bit numbers an . . . a2a1 and bn . . . b2b1;

• the approximate adder circuit comprising:
• a resistor and 2n+1 identical memristors;
• negative electrodes of the respective memristors are all connected to a same source line SL;
• one end of the source line SL is floating, and the other end is connected to one end of the resistor;
• n≥1;
• the control method comprising:
• selecting n memristors from the 2n+1 memristors, and writing logic values a1~an respectively;
• selecting one memristor from the remaining memristors, and writing an input carry c1;
• setting all other unset memristors to a high resistance state;
• executing n rounds of approximate addition sub-processes sequentially, wherein, in an i-th round of the approximate addition sub-process, the following operations are executed:
• in a first time period, a memristor written with a logic value ai is used as a first memristor, and a voltage −V is applied to a positive electrode thereof, a memristor storing the carry ci is used as a second memristor, and a positive electrode thereof is set to float, one memristor among the unset memristors is selected as a third memristor, a voltage VP is applied to a positive electrode thereof, and a voltage with an amplitude 0 is applied to the other end of the resistor, under the circumstances, carry ci+1=ai·bi is obtained from the third memristor;
• in a second time period after the first time period, a voltage V−VP is applied to the positive electrode of the first memristor, the voltage VP is applied to the positive electrode of the second memristor, the positive electrode of the third memristor is set to float, the voltage −V is applied to the other end of the resistor, under the circumstances, a sum result si=ai⊕bi+ci is obtained from the second memristor;
• wherein, i=1, 2, . . . , n, when a logic value bi is 0, a value of V is 0;
• when the logic value bi is 1, a value of V is VP;
• VP satisfies Vset/2<VP<Vset, and VP<2|Vreset|;
• Vset is a threshold for the memristor to convert from the high resistance state to a low resistance state;
• Vreset is a threshold for the memristor to convert from the low resistance state to the high resistance state;
• sn . . . s2s1 and cn+1 are an approximate addition result of the required n-bit numbers an . . . a2a1 and bn . . . b2b1.