194 A (7, 1/2) Convolutional Encoder

194 : A (7, 1/2) Convolutional Encoder

How it works

A Convolutional Encoder adds additional bits to a data stream or message that may later be used to correct errors in the transmission of the data. The specific implemented encoder is used in space applications and is a half-rate (R = 1/2) code with a constrain lenght of seven (K = 7). This means that the encoder generates two output bits (called symbols) for every input bit, and the encoder has m = K - 1 = 6 states.

How to test

Pull the write_not_shift input (IN1) high and set a 6-bit binary input (using IN3 to IN8), for example 0b100110. Provide a clock cycle on the clock input (IN0) to write the input into the shift register and clear the encoder. Pull the write_not_shift input (IN2) low to start shifting. Provide 12 clock cycles (6 input bits x 2 symbol bits = 12), after each clock cycle a 0 or 1 is displayed on the 8-segment display. The encoded output for the input 0b100110 is 0b101110010001 (left-to-right == first-to-last-bit displayed).


# Input Output
0 clock segment a
1 write_not_shift segment b
2 shift_input_0 segment c
3 shift_input_1 segment d
4 shift_input_2 segment e
5 shift_input_3 segment f
6 shift_input_4 segment g
7 shift_input_5 segment dp (used to indicate clock)