MC68HC11KW1 Datasheet, PDF (168/238 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

event counting mode of operation, in which the counter is clocked by an external source. In this
case, the prescaler is bypassed and the external signal is used to clock the Timer 2 counter
directly.
The input capture and output compare signals (OC1, OC2, OC3 and I1/OC4) are interfaced
through port J pins [7:4]. If the timer is configured for event counting mode, then port J pin 3 is
used as the input for the external clock. Refer to Figure 9-1 and Figure 9-3.
The Timer 2 counter can be read at any time, and can be reset to $0000 by writing any value to it
(in normal modes). In addition, the counter can be stopped and reset by setting the T2STP bit in
the TCTL4 register (see Section 9.2.8).
Timer 2 can be switched to event counting mode by writing to the ECEA and ECEB bits in the
TCTL4 register. When switching to event counting mode, the counter is not reset to zero, but
carries on from the state it was in at the time of switching. Immediately before the switch it was
sourced by the internal E clock, so the first 16-stage count cycle has an offset equal to the number
of E clock cycles after reset before the first write to TCTL4. The T2STP bit can be used to reset
the counter to zero, if required.
9
9-16
TIMING SYSTEM
MC68HC11KW1