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.
Pull the write_not_shift input (IN1) high and set a 6-bit binary input (using IN2 to IN7), 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 24 clock cycles (2 each for the 6 shift registers and 6 encoder registers 2x(6+6) = 24). After each clock cycle a 0 or 1 is displayed on the 8-segment display. The encoded output for the input 0b100110 is 0b10111|0010001101000111001. The first 6 bits of the encoded output may be discared.
| # | 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) |