255
H'FFFF
H'0000
STR0–STR4
OVF
TCNT value
Time
Figure 10.15 Free-Running Counter Operation
GR
H'0000
STR0–STR4
IMF
TCNT value
Time
Counter cleared by
GR compare match
Figure 10.16 Periodic Counter Operation
•
TCNT counter timing
Internal clock source: Bits TPSC2–TPSC0 in TCR select the system clock (CK) or one of three
internal clock sources (
φ
/2,
φ
/4,
φ
/8) obtained by prescaling the system clock. Figure 10.17
shows the timing.
External clock source: The external clock input pin (TCLKA–TCLKD) source is selected by
bits TPSC2–TPSC0 in TCR and its valid edges are selected with the CKEG1 and CKEG0 bits
in TCR. The rising edge, falling edge, or both edges can be selected. The pulse width of the
external clock signal must be at least 1.5 system clocks when a single edge is selected and at
least 2.5 system clocks when both edges are selected. Shorter pulses will not be counted
correctly. Figure 10.18 shows the timing when both edges are detected.
Summary of Contents for HD6417032
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Page 525: ...490 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 18 Self Refresh ...
Page 578: ...543 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 62 Self Refresh ...
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