Are all three hardware timers of the DS80C390 used by the TINI firmware?

Yes, all three are in use. The DS80C390 CPU used on the TINI has three 16-bit hardware timers/counters. The TINI firmware uses these three timers as follows:

• timer 0 Scheduler - 1ms per tick
• timer 1 Serial 1 clock
• timer 2 Serial 0 clock