MSU1 - SNES Media Streaming Unit
MSU1 - SNES Media Streaming Unit2020-01-11 15:03:02
MSU1 (Media Streaming Unit 1) is an enhancement for the SNES, adding support for full-motion video and CD-quality audio. It gives us a glimpse of what the ill-fated SNES PlayStation CD-ROM add-on would have allowed, only without the disc seeking latency.
Developer API Reference
Note: this is a skeleton section for now. It will be fleshed out more over time. Thank you for your patience! ^-^;
$2000 - MSU1_STATUS - Status Port
bit 0-2: MSU1 revision# bit 3: track missing flag bit 4: audio playing flag bit 5: audio repeat flag bit 6: audio busy flag bit 7: data busy flag
$2001 - MSU1_READ - Data Port
Returns data from the MSU1 data bus.
$2002 - $2007 - MSU1_ID - Identification
These six registers return the string
S-MSU1, which can be used to detect
the presence of the MSU1 expansion. If not found, fallbacks can be added:
skipping FMV sequences, using SPC700 audio, etc. In this way, software can
optionally support MSU1 enhancements while still also running on stock hardware.
$2002 'S' $2003 '-' $2004 'M' $2005 'S' $2006 'U' $2007 '1'
$2000 - $2003 - MSU1_SEEK - Data Address
Sets the address to read data from.
$2000 byte 0 $2001 byte 1 $2002 byte 2 $2003 byte 3 + trigger
$2004 - $2005 - MSU1_TRACK - Audio Track Number
Sets the audio track to play.
$2004 byte 0 $2005 byte 1 + trigger
$2006 - MSU1_VOLUME - Audio Volume
Sets the audio volume for MSU1 audio playback (linear scale.)
#$00 => 0% volume (muted) #$80 => ~50% volume (half volume) #$ff => 100% volume (normal volume)
$2007 - MSU1_CONTROL - Control
bit 0: playback enable bit 1: repeat enable bit 2-7: unused
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