I wired a very simple circuit on a breadboard using 2 switches as inputs, an xor chip with an led as the output. It worked fine, even when using pushbuttons the truth table was correct. But, when I replaced the xor with a xnor chip the little circuit did not work. The led lit immediately and stayed on while power was applied. The push button switches did not do anything.
Ok, now for the details of the components. The switches are spdt pushbuttons, wired as the following. Common from the first switch is the input, common from 2nd switch is the output, N O from 1st switch goes to N C on 2nd switch and NC on 1st switch is wired to N O on 2nd switch. The xor is a 4070 chip. I tied all of the unsued inputs to Vss. The xnor is a 4077 chip.
Why did the xor chip work and the xnor chip did not?
I really need some help!! Anybody got any answers or ideas?
The Tinker
Ok, now for the details of the components. The switches are spdt pushbuttons, wired as the following. Common from the first switch is the input, common from 2nd switch is the output, N O from 1st switch goes to N C on 2nd switch and NC on 1st switch is wired to N O on 2nd switch. The xor is a 4070 chip. I tied all of the unsued inputs to Vss. The xnor is a 4077 chip.
Why did the xor chip work and the xnor chip did not?
I really need some help!! Anybody got any answers or ideas?
The Tinker
