The 13th Design Contest in Okinawa・ Design Specification- 6
6. BCH encoder decoder system
This year’s design targeting system organization is shown in figure 8. The system is composed of ENCODER, DECODER and error counting module ERRCNT. You have to design DECODER and ERRCNT modules. Circuit synthesis target is only DECODER. ERRCNT is used only for the performance evaluation of BCD DECODER error correction capability.
Figure 8 : System organization
Description of ENCODER
ENCODER is transmission side, which generates 7 bit information as U(X) and 8 bit parity bits as R(x), then totally 15 bits SB(x) are generated.
In addition, ENCODER generates some errors inside and error-added 15 bits code also generated at the port SBWE (Send Bit With Error). START signal is also generated to show the beginning of 15 bit code. SB port is error free signal to let ERRCNT module to count total error numbers from DECODER.
Description of DECODER
DECODER is receiver side, which receives SBWE signal from ENCODER. Every 15 cycles, error correction operation is performed. The recovered data is sent out to RBEC（Received Bits Error Corrected） port. RBEC port outputs not only information bits but also parity bits to let ERRCNT count errors in both information and parity. START2 signal is generated to indicate the beginning position of the RBEC signal. START2 signal can be simple delayed signal of START by error correction latency.
Description of ERRCNT
This module is only for evaluation of DCODER error correction performance. Then you do not need to synthesize the circuit of ERRCNT. ERRCNT receives START and SB signals from ENCODER. Then It can always know true data. ERRCNT also receives START2 and RBEC signals from DECODER and compare RBEC and SB to count how many error bits are transferred. ERRCNT possess some big registers to count the total error bits and accumulated received bits. Those two information are transferred to outside by signals, ERRBITS and TOTBITS. By calculating the ratio ERRBITS/TOTBIT, bit error rate (BER) can be obtained. Since DECODER have some latency, please take the latency into account for your design.