All Questions
7
questions
1
vote
3
answers
117
views
Simple TTL: Is there a way to "detect" a high-z state and easily use that to drive other logic?
I have two TTL style logic chips, call them A and B (*), where the outputs of A are the inputs to B (think: 8 data lines). A has tri-state outputs, so when they are turned off they float. B is an ...
- 2,151
12
votes
4
answers
2k
views
When is it appropriate to mix 74LSxx components with original TTL 74xx?
I spend almost all my tinkering time with 1970s era logic circuits, which use almost all original 7400-series TTL. I do a fair bit of repair and am now starting to design additional logic to work with ...
- 2,151
3
votes
1
answer
910
views
Why does the 74LS08 see an input logic level even if the inputs are not connected?
I have an 74LS08 (AND gate.) I did not connect any inputs to the IC, but it gives me voltage at the outputs. Should I separate VSS?
0
votes
1
answer
314
views
Frequency counter schematic
I was wondering what's wrong with my Proteus schematic.
This schematic is supposed to show the frequency in Hertz on the display but instead only three zeroes are displayed.
Is there any component ...
- 3
0
votes
0
answers
70
views
Clear D flip flop internal logical scheme
I am new in this community and also in logic circuit design and digital electronics. I couldn't find the logical design on the internet for the following D flip flop and i would like to know how it's ...
- 101
0
votes
1
answer
919
views
Why is the output to this 74181 ALU circuit always on?
I recently built an ALU circuit using the 74181 4 bit ALU. The circuit I built is below:
simulate this circuit – Schematic created using CircuitLab
Please note that the pinout in the ...
- 807
0
votes
3
answers
265
views
How to switch one output between two buses
I'm looking to take the output of some registers (e.g. 74LS670) and have them each be able to output either to an A bus or a B bus, obviously only one register can output on each bus at one time. I'...
- 1