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Results tagged with digital-logic
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user 199993
Digital electronics treats discrete signals, unlike analog electronics which treats continuous signals. Digital logic is used to perform arithmetic operations with electric signals and constitutes the base for building CPUs.
32
votes
What is the simplest way to invert a signal with just one jumper?
Simplest way is to not invert the signal to begin with. Have the MCU firmware read the presence or absence of the jumper and based on that have the firmware consider the limit switch as normally close …
- 172k
2
votes
How to consider binary numbers?
How to interpret it depends on the context, and what operations are done to it. Most of the time with integer numbers, '1101' is either 13 (unsigned) or '-3' (signed in 2's complement), but extremely …
- 172k
0
votes
Calculator keypad detection technique
It is possible that the matrix is not scanned continuously by the calculator, but only when it detects a keypress. But it does not matter, just figure out for each button which two of the 11 wires it …
- 172k
1
vote
Accepted
Buffer before invert before buffer
A non-inverting buffer cannot be done directly, as the smallest building block you can make is an inverter, and two inverters make a buffer.
Two inverters in a row means it adds more delay, but it als …
- 172k
5
votes
Bandwidth required for an arbitrary digital signal
Frequency is not important, rise time is.
Ideal square waves have infinite bandwidth. Real-world square waves like your clock signal has some limited rate at which the signal changes (called slew rate …
- 172k
1
vote
Accepted
Is there any special reason behind the formula of radix complements? My concern is with whet...
If you think of say a bike odometer or a customer counter with for exampne 4 digits, you know it will count from 0000 to 9999 and then rolls over back to 0000, so they show the same count every 10000 …
- 172k
1
vote
Increment of 7 segment display value by 2
You will not be incrementing a symbol on a bunch of LEDs, but the value/number/bitpattern that gets encoded into a 7-segment symbol.
So basically, just add two to the value, in whatever form you store …
- 172k
2
votes
How is the PC reset on startup?
Most chips contain internal reset circuitry or then they require external reset circuitry to keep the chip in reset state until conditions such as supply voltage or clock have stabilized.
Reset is jus …
- 172k
4
votes
Is there a well-known digital logic circuit that outputs the last valid input on a high impe...
Yes there is. Many buffers have a feature called "bus hold".
- 172k
13
votes
Why should you not leave the inputs of unused gates floating with 74LS series logic?
The answer is not that different with 74LS than 74HC logic, but somewhat different.
HC logic inputs are high impedance so they must be set to high or low. They can't be left floating unconnected, beca …
- 172k
1
vote
Floating voltage on ROM CE
You can't expect to measure a microsecond level signal with multimeter.
Sure, the voltage could be 1.2V at DC, which is wrong, or the CPU could be executing from ROM as usual and it would have an aver …
- 172k
4
votes
Trick to recognize value of 2's complement number
Those are just bits representing a number in binary numeral system so they are powers of two and thus those are the weights in decimal of the binary bits.
It's really not any more complex than say 987 …
- 172k
2
votes
74LS74N did not work exactly as I expected
Likely the input voltages are wrong due to LEDs in parallel with the input.
- 172k
0
votes
We want numbers that lie between 1 and 10 inclusive, why should I use OR gate instead of AND?
If you think about it, your number can't be smaller than 1 and larger than 10 at the same time, so both conditions will not be true at the same time, but even one of the conditions mean there is an er …
- 172k
0
votes
Higher input voltage to a not gate
If it exceeds the nominal operating range, it might not work properly.
If it exceeds the absolute maximum ratings, it can be damaged.
- 172k