SH7708 Datasheet, PDF (332/633 Pages) Renesas Technology Corp – SuperH™ RISC engine

Auto-Reload Count Operation: Figure 11.3 shows the TCNT auto-reload operation.
TCNT value
TCOR
TCOR value set to
TCNT during underflow
H'00000000
STR0–STR2
UNF
Time
Figure 11.3 Auto-Reload Count Operation
TCNT Count Timing:
• Internal Clock Operation: Set the TPSC2–TPSC0 bits in TCR to select whether peripheral
module clock Pφ or one of the four internal clocks created by dividing it is used (Pφ/4, Pφ/16,
Pφ/64, Pφ/256). Figure 11.4 shows the timing.
Pφ
Internal
clock
TCNT
input clock
TCNT _{N + 1}
N
N–1
Figure 11.4 Count Timing when Internal Clock Is Operating
• External Clock Operation: Set the TPSC2–TPSC0 bits in TCR to select the external clock
(TCLK) as the timer clock. Use the CKEG1 and CKEG0 bits in TCR to select the detection
edge. Rise, fall or both may be selected. The pulse width of the external clock must be at least
1.5 peripheral module clock cycles for single edges or 2.5 peripheral module clock cycles for
both edges. A shorter pulse width will result in inaccurate operation. Figure 11.5 shows the
timing for both-edge detection.
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