This one was a bit of a tight squeeze, but i finally managed to get proper internal DIN sync built into a Boss DR110.
Normally when you add DIN sync to a DR110 you end up in a situation where you press play on your master device, the DR110 starts in sync, but when you press stop on the master and the DR110 stops, it doesn't reset to the start of the bar again. This means when you then press play again on the master, the DR110 just starts from where it stopped playing. You can get around this by pressing stop on the master clock, then pressing stop on the DR110 to reset it, then you have to press play on the DR110 to arm the sync again before pressing play on the master clock. As you can imagine, its not the ideal way of working.
I've spent the last couple of days figuring out how to work around this and have finally managed it by hacking some logic onto the run/stop DIN sync pin. Now when you press stop on the master the DR110 stops, automatically resets itself and re-arms the play to wait for another start signal. Nice!
UPDATE: We now have some internal DIN sync kits available for the DR110 at
http://www.circuitbenders.co.uk/forsale/DR110sync.html