• Although CD-DA can be used as a sound source in Saturn, there are some precautions to be taken when playing a CD.
  First, the data of the CD-DA is always input to the SCSP, mixed under the same control as other sounds, and then output, so even when playing the CD-DA, the mixing balance and localization settings should be set. You have to do it right.

• Please note that if you make a mistake in the settings, the sound may be clipped and distorted, or the sound may not be output correctly in stereo.

• Basically, from the perspective of SCSP, CD-DA is handled in exactly the same way as one sound of a PCM sound source, so if you mainly fully understand the function of the "MIXER register", mistakes will disappear. I think.

• Here, I would like to briefly explain how to play a CD-DA in stereo.
  The following is also the basis for handling SCSP digital mixers, so if you are dealing with SCSP, please read it.

• Figure 3.1 shows the route from when the CD-DA is input to the SCSP to when it is output, so we will explain based on that.

Figure 3.1 CD-DA route

• As shown in Fig. 3.1, the CD-DA is first controlled by the output level, then panned (localized between LRs), and then mixed with other sound sources (PCM / FM sound with built-in SCSP). Is received and combined into a stereo output.
  Finally, it is output under the output level control by MVOL (master volume).

• There are five registers that must be set when outputting a CD-DA.

  First, "EFSDL16 / 17" to balance the level between each sound source, "EFPAN16 / 17" to specify the localization of each sound source, and finally "MVOL" to adjust the output level.

• The register named ~ SDL is a register that adjusts the level balance of each sound, and is an image of a slide fader in a mixer.

• The volume control in SCSP is basically a damping adjustment type. The attenuation adjustment type is a method of adjusting the volume in the direction of reducing the volume when balancing with other sound sources.

  The reason for adopting this method is that Saturn does not have an amplifier, so the volume cannot be raised, so if the dynamic range cannot be adjusted to be as wide as possible, the volume will be very low. Because it will end up.

• The register named ~ PAN is a register that adjusts the localization of each sound, and is a pan pot in a mixer.

• The pan pot can be set to 31 levels of localization between LRs.

• It is a register for adjusting all sound output levels of Satan as well as CD-DA. (4 bit configuration)

• If this register value is set to "0H", no sound will be output, so be sure to set it to a value other than "0H" when producing sound.
  Normally, set it to "FH" (= 0 [dB] = no attenuation = maximum volume).

• Based on the above, I would like to explain the settings for outputting a CD-DA.

• First, set the output level of the CD.

  If only the CD-DA outputs sound, there is no other mixing sound, so the level can be 0 [dB], so set EFSDL16 / 17 to "7H" respectively.

  If you want to make other sounds, lower the level to prevent overflow. (By the way, if you decrease the value, the volume will decrease.)

• Next, set the pan pot (localization).

  What you have to be careful about when outputting a CD-DA is that when it comes to a CD-DA, it is divided into LR (left and right channels) and input to the SCSP, but on the SCSP side it is the same as the sound of the PCM sound source / FM sound source. If you do not set the panning correctly, the L channel side will be L and the R channel side will be R, so even if the CD-DA is stereo, it will not actually be output in stereo. I will end up.

  Therefore, set "1FH" for "EFPAN16" and "0FH" for "EFPAN17". (For data on the localization position with respect to the register settings, refer to the "Mixer" section below.

• Next, set the master volume (“MVOL”).

  Since this is the master volume of the final stage, set it to the maximum volume "FH" for the time being.

  The settings up to now are summarized in Table 3.1 below.

• With the above settings, you will be able to output a CD-DA.

However, if you want to make it monaural, set the EFSDL value to one smaller than the stereo setting.