h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 379

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

12.3
12.3.1
TCNT is incremented by input clock pulses (either internal or external).
Internal Clock: An internal clock created by dividing the system clock ( ) can be selected by
setting bits CKS2 to CKS0 in TCR. Figure 12.2 shows the count timing.
External Clock: Three incrementation methods can be selected by setting bits CKS2 to CKS0 in
TCR: at the rising edge, the falling edge, and both rising and falling edges.
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.
Figure 12.3 shows the timing of incrementation at both edges of an external clock signal.
Internal clock
TCNT input
clock
TCNT
Operation
TCNT Incrementation Timing
Figure 12.2 Count Timing for Internal Clock Input
N – 1
N
Rev. 4.00 Jun 06, 2006 page 325 of 1004
Section 12 8-Bit Timers
REJ09B0301-0400
N + 1