I am frequently asked "How many tracks is it possible to arm using Sony protocol?"
Using the Sony P2 protocol the maximum tracks that can be armed is 112 calculated as follows
Maximum number of data bytes = 15
One bute is used for analog audio, video and Insert or Assemble
14 bytes may be used for track arming 14*8 = 112
The track arm tally request command includes a byte with a byte specifying offset and length making it is possible to request more track arm tallies but this is not normally used.
Not all manufactures have implemented 112 tracks, within CB the RM-6 and SR-4 support 96 tracks, The UR-422 and UR-422usb support 64 tracks. CBServer currently supports 80 tracks which will soon be increased to 96 tracks. Until recently Pro-Tools supported a maximum of 48 Tracks.
When I originally designed the SR-4 8 or 16 record tracks per machine was standard (DA-88,DD-8...) I provided system track arming to cope with recording onto multiple machines by allowing each record key to be routed to any track on any machine.
With advances in computer hardware it is now common place to have a single record machine with 64 tracks and 96 or more are being discussed.
This question came up recently at Twickenham studios, the AMS-Neve DFC MCS supports a maximum of 48 tracks on each output port, paradoxically the DFC supports 96 track arms internally. To use all 96 tracks it is necessary to use two output ports.
To cope with the limited track arm capability of the DFC output ports CB have written software so that two DFC-MCS ports are connected to two inputs on the X-4 software. An extra option has been added allowing the track arming on une input to be offset by 48 tracks.