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CHAPTER 14 FREQUENCY COUNTER
User’s Manual U15104EJ2V0UD
Figure 14-6. Gate Timing of Frequency Counter
(a) If gate time is set to 1, 4, or 8 ms
(b) If gate is set to be open
Caution
If counting is started by using IFCST while this gate is open, the gate is closed after an undefined
time. To open the gate, therefore, do not set IFCST to 1.
Remark
IFCST:
Bit 1 of IF counter control register (IFCCR)
IFCJG0:
Bit 0 of IF counter gate judge register (IFCJG)
IFCCK1, 0: Bits 1 and 0 of IF counter mode select register (IFCMD)
H
L
Internal 1 kHz
IFCJG0
Sets IFCST.
IFCJG0 is automatically set at this point.
Counting starts.
Gate is opened at this point.
Clears
IFCJG0
Counting ends
if gate time is
8 ms.
Gate time: 8 ms
Gate time: 1 ms
Gate time: 1 ms
Counting ends if gate time is 1 ms.
Counting ends if gate time is 4 ms.
1 ms
4 ms
8 ms
OPEN
CLOSE
OPEN
CLOSE
OPEN
CLOSE
Gate time
Count period.
If IFCST is set during this period,
gate is closed after undefined time.
H
L
Internal 1 kHz
Gate
Gate
IFCCK1 = IFCCK0 = 1.
Gate is opened at this point.
If gate is opened when IFCJG0 is opened, gate is closed after undefined time.
IFCCK1 = IFCCK0 = 1
Sets gate time by using IFCCK1 and IFCCK0
Count period
OPEN
CLOSE
OPEN
CLOSE
Содержание mPD178053
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