[sdiy] Pro One CEM3340 Sync magic

[MTG]

I had an interesting discovery this weekend (for me anyway). As I'm sure 
many of you know, the Pro One has a single (free-running I call it) LFO and 
this lone LFO also drives the sequencer/arpeggiator.  While working on my 
"replacement CPU" I noticed, that while the LFO was free running, it would 
always sync to the user when they first played notes with the Arp on. That 
is, the first note would sound immediately and then the LFO would clock the 
next note one LFO period later. My initial attempts at duplicating the 
arpeggiator resulted in no note sounding until the LFO "came around" to the 
proper edge used to clock the notes. So I'm thinking, how the hell do they 
reset the LFO to the user?  Low and behold they used a rather clever method 
of squashing the triangle wave of the 3340 which resets the LFO. This seems 
to be somewhat undocumented since the part has other pins for sync. Anyway I 
guess it's more well  known to others, since today I found a mention of it 
in this thread:

http://electro-music.com/forum/post-176134.html

GB
www.musictechnologiesgroup.com