Abstract: For solving the problem that the original digital bidirectional function is insecurity when processing the low-byte data, a novel configurable low-byte digital bidirectional function is proposed. First of all, in order to improve the security of the method, the address information is added as a chaotic data between hierarchies. Next, adding the reverse mode ensures the variability of chaotic data. And the two new improvements are configurable by the user, which further enhances security. Finally, the secure RISC-V processor framework is built using the improved method and simulated on a Virtex 7-based FPGA. Experiments show that the randomness performance, the avalanche effect, the input-output correlation and the output-output correlation of processing low-byte data are improved by using the new method.