9-2 DSP Function and MAC Instruction There are 2 functions in multiplication and accumulation. One is the MAC instruction which can be used in the entire SuperH family. The MAC instruction transfers data, multiplies that data and executes accumulation with the MAC register in 1 instruction. The instructions and data use a common bus, so it requires 2 or 3 clock cycles. However, the SH3-DSP DSP function transfers 2 data items from memory to the DSP data register in 1 clock cycle, at multiplying between DSP data registers in 1 clock cycle and accumulating in 1 clock cycle. It takes 3 clock cycles to complete multiplication and accumulation for the initial data, but data operations are pipelined so subsequent multiplication and accumulation results are obtained in 1 clock cycle. This is the same performance at the general DSP. The instruction that uses the DSP function specifies 2 data transfers and multiplication operations, and subtraction and addition circuit operations. For that reason the DSP function instruction is extended to 32 bits.