Reducing power consumption of instruction ROMs by exploiting instruction frequency

This paper proposes a new approach to reducing the power consumption of instruction ROMs for embedded systems. The power consumption of instruction ROMs strongly depends on the switching activity of bit-lines. If a read bit-value indicates ’0’, the precharged bitline is discharged. In this scenario, a bit-line switching takes place and consumes power. Otherwise, the precharged bit-line level is maintained until the next access, thus no bit-line switching occurs. In our approach, the binary-patterns to be assigned to op-codes are determined based on the frequency of instructions for reducing the bit-line switching activity. Application programs are analyzed in advance, and then binarypatterns including many ’1’ are assigned to the most frequently referenced instructions. In our evaluation, it is observed that the proposed approach can reduce 40% of bit-line switching.