Datasheet

Section 13 8-Bit Timers (TMR)
Rev. 3.00 Mar 17, 2006 page 637 of 926
REJ09B0283-0300
TCNT
H'FF
Counter clear
TCORA
TCORB
H'00
TMO
Figure 13.2 Example of Pulse Output
13.5 Operation Timing
13.5.1 TCNT Incrementation Timing
Figure 13.3 shows the count timing for internal clock input. Figure 13.4 shows the count timing
for external clock signal. Note that the external clock pulse width must be at least 1.5 states for
incrementation at a single edge, and at least 2.5 states for incrementation at both edges. The
counter will not increment correctly if the pulse width is less than these values.
φ
Internal clock
Clock input
to TCNT
TCNT
N–1 N N+1
Figure 13.3 Count Timing for Internal Clock Input