Tested with a 358-state 3-mixture 27-feature
800-word HMM, S3C44b0X operates at 40 MHz and coprocessor
at 10 MHz to meet the real-time requirement, and the recognition
accuracy is 95.2%. Power consumption of the micro-controller
is 10mW, and that of the coprocessor 15.2 mW. The overall
speech recognition system achieves the lowest energy consumption
per word recognition among many reported designs. Experiment
and analysis show that the speech recognition system based on the
proposed coprocessor is especially suitable for mid-size vocabulary
(100–1000 words) recognition tasks.
Index Terms—Coprocessor, custom design, field-programmable
gate array (FPGA), hardware implementation, hidden