H8S2245 datasheet(416/818 Pages) RENESAS

tên linh kiện	H8S2245

Giải thích chi tiết về linh kiện	Renesas 16-Bit Single-Chip Microcomputer H8S Family / H8S/2200 Series

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Section 10 8-Bit Timers

Rev.3.00 Mar. 26, 2007 Page 374 of 772

REJ09B0355-0300

10.3

Operation

10.3.1

TCNT Incrementation Timing

TCNT is incremented by input clock pulses (either internal or external).

Internal Clock

Three different internal clock signals (

φ/8, φ/64, or φ/8192) divided from the system clock (φ) can

be selected, by setting bits CKS2 to CKS0 in TCR. Figure 10.2 shows the count timing.

Internal clock

Clock input

to TCNT

TCNT

N–1

N+1

Figure 10.2 Count Timing for Internal Clock Input

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 10.3 shows the timing of incrementation at both edges of an external clock signal.

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