194 A (7, 1/2) Convolutional Encoder
194 : A (7, 1/2) Convolutional Encoder
- Author: Jos van 't Hof
- Description: A (7, 1/2) Convolutional Encoder following the CCSDS 131.0-B-4 standard.
- GitHub repository
- Clock: 0 Hz
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).
IO
| # | 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) |