Program decoders

Avast Free Security. WhatsApp Messenger. Talking Tom Cat. Clash of Clans. Subway Surfers. TubeMate 3. Google Play. Canon ink cartridge. Beanie Babies movie on Apple. Twee's return on TikTok. Windows Windows. Most Popular. New Releases. Desktop Enhancements. Networking Software. Trending from CNET. The circuit diagram of 2 to 4 decoder is shown in the following figure. If enable, E is zero, then all the outputs of decoder will be equal to zero. In this section, let us implement 3 to 8 decoder using 2 to 4 decoders.

We can find the number of lower order decoders required for implementing higher order decoder using the following formula. Therefore, we require two 2 to 4 decoders for implementing one 3 to 8 decoder. The block diagram of 3 to 8 decoder using 2 to 4 decoders is shown in the following figure.

The complement of input A 2 is connected to Enable, E of lower 2 to 4 decoder in order to get the outputs, Y 3 to Y 0. These are the lower four min terms. The input, A 2 is directly connected to Enable, E of upper 2 to 4 decoder in order to get the outputs, Y 7 to Y 4.

These are the higher four min terms. In this section, let us implement 4 to 16 decoder using 3 to 8 decoders. Therefore, we require two 3 to 8 decoders for implementing one 4 to 16 decoder. To overcome this, we use Priority Encoders. Another ambiguity arises when all inputs are 0. In this case, encoder outputs which actually is the output for D0 active. In order to avoid this, an extra bit can be added to the output, called the valid bit which is 0 when all inputs are 0 and 1 otherwise.

Priority Encoder — A priority encoder is an encoder circuit in which inputs are given priorities. When more than one inputs are active at the same time, the input with higher priority takes precedence and the output corresponding to that is generated. Let us consider the 4 to 2 priority encoder as an example. From the truth table, we see that when all inputs are 0, our V bit or the valid bit is zero and outputs are not used.

Here, D3 has highest priority, therefore, whatever be the other inputs, when D3 is high, output has to be And D0 has the lowest priority, therefore the output would be 00 only when D0 is high and the other input lines are low.

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