Creating Boolean sequence using SPDT switches

Question

I am experimenting with digital counters and for one application it would be useful to generate a set of four pairs of 3-bit values used for comparing (Cx) and resetting (Rx) a counter. Since there are four possible outputs I think that it's possible to use two SPDT switches (Sx) that can be connected to GND and VCC to create these values.

Proposed truth table:

Calculating Cx and Rx values can be easily done with standard logic gates as follows:

C2= (¬S1) and (¬S0) = S1 nor S0;

C1= S1 xor S0;

C0 = S0;

R2 = 0;

R1 = ¬S1;

R0 = ¬S0;

In terms of used components (4000-series ICs) this would require a Hex Inverter (CD4049), a XOR Gate (CD4070) and either a NOR gate (CD4001) or an AND Gate (CD4081). Total of 3 ICs.

I was wondering if there is a more elegant solution for such a simple task. Perhaps problematic C2 and C1 value can be generated using discrete components. I would appreciate any improvement suggestions.

Answer 1

use instead multipole switches:

^{simulate this circuit – Schematic created using CircuitLab}

Or use and gates and iverters.

^{simulate this circuit}

or use all nand gates.

^{simulate this circuit}

Answer 2

Come to think of it, it seems that this can be accomplished using only one XOR gate IC and couple of passives:

C2= (¬S1) and (¬S0) = S1 nor S0 = (S1 or S0) xor 1; \ XOR used as an inverter

C1= S1 xor S0;

C0 = S0;

R2 = 0;

R1 = ¬S1 = S1 xor 1; \ XOR used as an inverter

R0 = ¬S0 = S0 xor 1; \ XOR used as an inverter

OR gate needed for C2 can be accomplished with two diodes and pull down resistor.

So my proposed schematic is as follows: