#Proteus 8 rotary encoder code#

Here for example, the angular or rotary position of a compass is converted into a digital code by a 74LS148 8-to-3 line priority encoder and input to the systems computer to provide navigational data and an example of a simple 8 position to 3-bit output compass encoder is shown below. Positional EncodersĪnother more common application is in magnetic positional control as used on ships navigation or for robotic arm positioning etc. Keypad encoders such as the 74C923 20-key encoder are available to do just that.

The 104 individual buttons or keys could be encoded into a standard ASCII code of only 7-bits (0 to 127 decimal) to represent each key or character of the keyboard and then input as a much smaller 7-bit B.C.D code directly to the computer.

#Proteus 8 rotary encoder Pc#

Another alternative and better way would be to interface the keyboard to the PC using a priority encoder. One way would be to connect all 104 wires from the individual keys on the keyboard directly to the computers input but this would be impractical for a small home PC. For example, assume that a microcomputer needs to read the 104 keys of a standard QWERTY keyboard where only one key would be pressed either “HIGH” or “LOW” at any one time. Priority encoders can be used to reduce the number of wires needed in a particular circuits or application that have multiple inputs. Digital Encoder using Logic Gatesĭigital Encoder Applications Keyboard Encoder We can constructed a simple encoder from the expression above using individual OR gates as follows. In practice these zero inputs would be ignored allowing the implementation of the final Boolean expression for the outputs of the 8-to-3 priority encoder. Where X equals “dont care”, that is it can be at a logic “0” level or at a logic “1” level.įrom this truth table, the Boolean expression for the encoder above with data inputs D 0 to D 7 and outputs Q 0, Q 1, Q 2 is given as: The truth table for a 8-to-3 bit priority encoder is given as: Digital Inputs Once input “ D5” had been removed the next highest output code would be for input “ D3” (“011”), and so on. Priority encoders output the highest order input first for example, if input lines “ D2“, “ D3” and “ D5” are applied simultaneously the output code would be for input “ D5” (“101”) as this has the highest order out of the 3 inputs. Priority encoders are available in standard IC form and the TTL 74LS148 is an 8-to-3 bit priority encoder which has eight active LOW (logic “0”) inputs and provides a 3-bit code of the highest ranked input at its output. So when an input with a higher priority is present, all other inputs with a lower priority will be ignored. The priority encoders output corresponds to the currently active input which has the highest priority. The Priority Encoder solves the problems mentioned above by allocating a priority level to each input. Then this type of digital encoder is known commonly as a Priority Encoder or P-encoder for short. So if there is more than one input at logic level “1” at the same time, the actual output code would only correspond to the input with the highest designated priority.

One simple way to overcome this problem is to “Prioritise” the level of each input pin. Also, an output code of all logic “0”s can be generated when all of its inputs are at “0” OR when input D 0 is equal to one. For example, if we make inputs D 1 and D 2 HIGH at logic “1” both at the same time, the resulting output is neither at “01” or at “10” but will be at “11” which is an output binary number that is different to the actual input present. One of the main disadvantages of standard digital encoders is that they can generate the wrong output code when there is more than one input present at logic level “1”. The output lines of a digital encoder generate the binary equivalent of the input line whose value is equal to “1” and are available to encode either a decimal or hexadecimal input pattern to typically a binary or “B.C.D” (binary coded decimal) output code. An “n-bit” binary encoder has 2 n input lines and n-bit output lines with common types that include 4-to-2, 8-to-3 and 16-to-4 line configurations. Generally, digital encoders produce outputs of 2-bit, 3-bit or 4-bit codes depending upon the number of data input lines. So we can say that a binary encoder, is a multi-input combinational logic circuit that converts the logic level “1” data at its inputs into an equivalent binary code at its output. The Digital Encoder more commonly called a Binary Encoder takes ALL its data inputs one at a time and then converts them into a single encoded output. The job of a priority encoder is to produce a binary output address for the input with the highest priority. Unlike a multiplexer that selects one individual data input line and then sends that data to a single output line or switch.