The NTE is a monolithic 4-line-toline decoder in a Lead DIP type The NTE is fully compatible for use with most other TTL and DTL circuits. MOS technology. A binary code applied to the four inputs (A to D) provides a low level at the selected one of sixteen outputs excluding the other fifteen outputs. SNN .. of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration.
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Post as a guest Name. The active-low enable inputs allow cascading of demultiplexers over many bits. There are probably two enable inputs because otherwise there eatasheet be two unused pins on the 24 pin package I don’t recall seeing 22 datasheet DIP packages.
So is it possible that both enables are hooked to a 2-input OR gate; this is just making use of the extra pins to make 24? The demultiplexing function is performed by using the 4 input lines to address the output line, passing data from one of the strobe inputs with the other strobe input low.
When either strobe input is high, all outputs are high. This allows more flexibility in the logic functions dagasheet. My first question is more important Understand, this is a typical example of application, not it’s sole purpose.
Sign up using Facebook. The LED can be chosen at random by the status of the 4 line selector inputs. First, the inversion of the outputs simply means that the output is active low.
For example, if the target application requires 16 7-segment LED displays, but your microcontroller only has 4 lines to select which display is active, this chip 74LS would provide a very effective method of essentially multiplying you selecting lines by a 4 times.
All inputs are buffered and input clamping diodes are provided to minimize transmission-line effects and thereby simplify system design. Datasueet 49k 2 28 Email Required, but never shown.
Many TTL parts and older memory chips have active low enable inputs, so the active low outputs of this part can be connected directly to those inputs.
74154 Datasheet PDF
Each or these 4-line-toline decoders utilizes TTL circuitry to decode four binary-coded inputs into one of sixteen mutually exclusive outputs when both the strobe inputs, G1 and G2, are low. Please consider upvoting those questions you found useful like this one by clicking the arrow pointing up near the answer vote count which is in turn above the checkbox you clicked to accept this question. As for the NAND gates, there is a function being implemented in which the gates are there to realize it.
That is, if the outputs were active high, OR gates would perform the synthesis desired. Sign up or log in Sign up using Google.
National Semiconductor – datasheet pdf
The person who took time to answer the question will appreciate that. Home Questions Tags Users Unanswered. Since the ouputs are active low, NAND gates do the job.
This chip is often used in demultiplexing applications, such as digital clocks, LED matrices, and other graphical outputs. Rather than providing only a single enable, both pins are used. Each of the datasehet outputs can be connected through a resistor and then through an LED to serve as a simple 16 LED controller.
And why are there 2 of them, you ask? That is, for an input ofthe 0 output is selected, darasheet it is driven low. Download the datasheet below for a more comprehensive summary. However, due to the internal structure of theonly one output can be enabled at a time.
Datasheet(PDF) – National Semiconductor (TI)
The active-low output is just how the design for that specific decoder was carried out – there is also active-high varieties. If you wanted to generate a 1 of demultiplexer, you could use 16 s looking at the 4 least significant bits, while a single would look at the 4 most significant bits, with one ouput going to each of the other 16 s.
These demultiplexers are ideally suited for implementing high-performance memory decoders.