They aren't called AND, OR, NAND, NOR, Exclusive OR or NOR, they have different names , what are they called?
They aren't called AND, OR, NAND, NOR, Exclusive OR or NOR, they have different names , what are they called?
It's just a matter of drawing styles. Instead of a NAND gate (AND gate with inverter outputs) you can place an OR gate with inverters in front. You'll find the inverted input notation often in complex logic symbols to visualize the active level of the respective pin.But I was shocked to see negative logic inverters at the outputs on the CD4017 datasheet by Texas Instruments.
Yes, you can think of it as being an inverter between the pin and the internal logic but from a design point of view that only complicates things.
estimation of gate delays.
There's an internal inverter pair (apparently to compensate delays)
A gate delay is the time difference between the input state changing and the output responding. All gates (in fact all components) introduce a small delay because to change internal voltages the capacitors formed across all the insulating layers in the silicon have to discharge and recharge. It's an RC thing again but please don't start querying it again. Just accept the delay is there and it is VERY short.
If they meet up again the signals will be slightly out of step. Occasionally a manufacturer will deliberately add gates, for example several inverters in a chain so the signals leaving the IC line up with each other.
The datasheet for an ordinary CD4xxx series Cmos logic gate shows its propagation delay. Why didn't you look?
I worked with old TTL about 39 years ago. It is obsolete now. The propagation delay of logic ICs is so small that I never had a problem with it and I never thought about it.So does CMOS LOGIC gates have more or less Propagation delay than TTL logic gates?
The concept of using RC networks to compensate for propagation delays, especially ones with with diodes is absolute nonsense. The delays we are talking about here are are incredibly small and in any case built inside the IC.
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