HD6433640 HITACHI [Hitachi Semiconductor], HD6433640 Datasheet - Page 268

• Manufacturer Part Number: HD6433640
• Description: H8/3644 Series Hardware Manual
• Manufacturer: HITACHI [Hitachi Semiconductor]

FRC Count Timing: FRC is incremented by clock input. Bits CKS1 and CKS0 in TCRX can
select one of three internal clock sources (ø/2, ø/8, ø/32) or an external clock.
260
Internal clock
Bits CKS1 and CKS0 in TCRX select one of three internal clock sources (ø/2, ø/8, ø/32)
created by dividing the system clock (ø). Figure 9.20 shows the increment timing.
External clock
External clock input is selected when bits CKS1 and CKS0 are both set to 1 in TCRX. FRC
increments on the rising edge of the external clock. An external pulse width of at least 1.5
system clocks (ø) is necessary. Shorter pulses will not be counted correctly. Figure 9.21 shows
the timing.
ø
FTCI
(external clock
input pin)
FRC input
clock
FRC
ø
Internal
clock
FRC input
clock
FRC
N – 1
Figure 9.21 Increment Timing with External Clock
Figure 9.20 Increment Timing with Internal Clock
N
N
N – 1
N + 1