TCON : Counter/Timer CONtrol Register
TF1, TF0 :
Overflow flags for Timer 1 and Timer 0.
TR1, TR0 :
Run control bits for Timer 1 and Timer 0.
Set to run, reset to hold.
IE1, IE0 :
Edge flag for external interrupts 1 and 0. *
Set by interrupt edge, cleared when interrupt is processed.
IT1, IT0 :
Type bit for external interrupts. *
Set for falling edge interrupts, reset for 0 level interrupts.
* = not related to counter/timer operation but used to detect
and initiate external interrupts.