A decoder is a circuit which has n inputs and 2n outputs, and outputs 1 on the For example, a decoder might be drawn like this: Here is a decoder. The MC74LCX is a high performance, 3-to-8 decoder/demultiplexer operating from a to V supply. High impedance TTL compatible inputs significantly. DESCRIPTION. The M74HC is an high speed CMOS 3 TO 8. LINE DECODER fabricated with silicon gate. C2MOS technology. If the device is enabled, 3.
|Published:||9 February 2014|
|PDF File Size:||39.44 Mb|
|ePub File Size:||43.47 Mb|
A 3-to-8 line decoder activates one of eight output bits for each input value from 0 to 7 — the range of integer values that can be expressed in three bits.
Similarly, a 4-to line decoder activates one of 16 outputs for each 4-bit input in the integer range [0,15]. A BCD to decimal decoder has ten output bits. It accepts an input value consisting of a binary-coded decimal integer value and activates one specific, unique output for every input value in the range [0,9].
Two active-low and one active-high enable inputs reduce the 3 to 8 decoder for external gates or inverters when expanding.
A line decoder can be implemented without external inverters and a 3 to 8 decoder decoder requires only one inverter. An enable input can be used as a data input for demultiplexing applications. Many components have an Enable input which works in this way.
MC74LCX Low Voltage CMOS 3-to-8 Decoder/Demultiplexer
Exercise How must the circuit be modified to make the Enable input active low? Multiplexers A multiplexer is a device which allows one of a number of inputs to be routed to a single output.
Here is a multiplexer. If c1c0 represents the number n in binary, then the value of the output d is the value of input in. Multiplexers are useful in many situations.
CD74HC High Speed CMOS Logic 3-to-8 Line Decoder Demultiplexer with Address Latches |
For example, in a CPU, data being written to memory might come from one of a number of sources - from a register, from the result of a calculation, etc - so a multiplexer would be used to 3 to 8 decoder data from the appropriate source.
Another application is where we 3 to 8 decoder to be able to choose one of several operations to carry out on some data - all the operations can be calculated, and a multiplexer can be used to select the desired result more on this later.
Implementing Multiplexers The implementation of a multiplexer is straightforward, and uses a decoder. All the outputs of the decoder are 0, apart from one. The inputs c1c0 determine which of the outputs is non-zero.
High Speed CMOS Logic 3-to-8 Line Decoder Demultiplexer with Address Latches
All but one of the AND gates have 0 on one input and therefore output 0. The remaining AND gate has 1 on one input and in where n is represented in binary by c1c0 on the 3 to 8 decoder input.
The output of this AND gate is the value of in. The OR gate has 0 on all of its inputs apart from one, and has the value of in on the remaining input.
The output of the OR gate is therefore the value of in.