1. 1 Inputs: q (quarter), d (dime) and n (nickel) Input can be two bit coded input or three bit not coded input –Two bit coded: 00 no coin, 01 nickel, 10 dime, and 11 quarter –Three bit not coded: 001 nickel, 010 dime, and 100 quarter Suppose, we can ask the coin slot to directly return if we cannot accept an input coin –We do this by issuing a signal return coin (rc) We also generate an output return nickel (rn) and return dime (rd) We also generate an output to release product (rp) States: S00, S05, S10, S15, S20, S25, S30, S35, S40, S45, S50 –Notice the names (they need not be S0, S1….) –We also may have S30’ and S35’ where we return coins (we do not need to return in any other state) Design of Complex Wending Machine

2. 2 State Changes in Wending Machine S35’ S00 S15S45S35S05S25 S20S50S40S10S30 S30’ n q d n d q n d q n d q n d q n d q n d q n d q n d q n d q Outputs (rc, rn, rd, rp) = (0, 0, 0, 0) in S00, S05, S10, S15, S20, S25, S30, S35 Outputs (rc, rn, rd, rp) = (1, 0, 0, 0) in S30’ and S35’ Outputs (rc, rn, rd, rp) = (0, 0, 0, 1) in S40 Outputs (rc, rn, rd, rp) = (0, 1, 0, 1) in S45 Outputs (rc, rn, rd, rp) = (0, 0, 1, 1) in S50

3. 3 Multiplexers is a circuits which selects one of many inputs First let us assume that we have one bit inputs And we have eight inputs, I0, I1, I2, I3, I4, I5, I6, I7 We want one of them to be output based on selection signal We need a 3 bit select input to decide which input goes to output Note the order of select signals –X is MSB and Z is LSB Multiplexing and Multiplexer S2 S1 S0 F 0 1 2 3 4 5 6 7 I0 I1 I2 I3 I4 I5 I6 I7 XYZXYZ

4. 4 We can write a logic equation for output F as follows F = X’ Y’ Z’ I0 + X’ Y’ Z I1 + X’ Y Z’ I2 + X’ Y Z I3 + X Y’ Z’ I5 + X Y’ Z I6 + X Y Z’ I6 + X Y Z I7 This circuit can be implemented using –8 four-input AND gates and one OR gates Multiplexer Design S2 S1 S0 F 0 1 2 3 4 5 6 7 I0 I1 I2 I3 I4 I5 I6 I7 XYZXYZ

5. 5 Multiplexers can be directly used to implement as a circuit Easiest way is to use function input as selection signals Input to multiplxer is a set of 1s and 0s depending on the function to be implemented We use a 8 to 1 multiplexer to implement function F Three select signals are X, Y, and Z, and output is F Eight inputs to multiplexer are 1 0 1 0 1 1 0 0 Depending on the input signal –multiplexer will select proper output Designing with multiplexers S2 S1 S0 F 0 1 2 3 4 5 6 7

6. 6 Suppose we want to design a rotate circuit Inputs are i3 i2 i1 i0 Output is zero, one, two, or three bit rotated output Rotation can be in left or in right direction Four sets of outputs are –i3 i2 i1 i0 –i2 i1 i0 i3 –i1 i0 i3 i2 –i0 i3 i2 i1 Input/Output relations ship is given in the table We can implement this circuit using four 4 to 1 multiplexers Using Multiplexers S1 S0 F 0 1 2 3