P4 execution instruction (01h) initializes the DSP unit with a built-in sound source. In practice, the following data is set in the DSP register to turn off the effect component output and prohibit the DSP from accessing (R / W) the D-RAM. At this time, initialization of the mixer is also executed, but it is restored. This has no effect on other sounds (sequence playback, CD-DA playback, PCM stream direct components).
[IMXL] <--- 00H
[EFSDL],[EFPAN] <--- 00H
[MPRO] <--- 00000000H
[COEF] <--- 000H
[TEMP] <--- 000000H