BIT  NAME     FUNCTION
  ---  ----     --------
   0   start    1 = start timer a, 0 = stop timer a.
                    This bit is automatically reset (= 0) when
                    underflow occurs during one-shot mode.
   1   pbon     1 = timer a output on pb6, 0 = pb6 is normal operation.
   2   outmode  1 = toggle, 0 = pulse.
   3   runmode  1 = one-shot mode, 0 = continuous mode.
   4   load     1 = force load (this is a strobe input, there is no
                    data storage;  bit 4 will always read back a zero
                    and writing a 0 has no effect.)
   5   inmode   1 = timer a counts positive cnt transitions,
                0 = Timer A counts 02 pulses.
   6   spmode   1 = serial port=output (cnt is the source of the shift
                    clock)
                0 = Serial port=input  (external shift clock is
                    required)
   7   UNUSED