PD17012_15 Datasheet, PDF (205/320 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DIGITAL TUNING SYSTEM HARDWARE

µPD17012, 17P012
17.3.2 Operation of gate when IF counter function is selected
(1) When gate time of 1, 4, or 8 ms is selected
The gate is opened for 1, 4, or 8 ms from the rising of the internal 1 kHz signal after the IFCSTRT flag has
been set to 1, as illustrated below.
While this gate is open, the frequency input from a selected pin is counted by a 16-bit counter.
When the gate is closed, the IFCG flag is cleared to 0.
The IFCG flag is automatically set to 1 when the IFCSTRT flag is set.
H
Internal 1 kHz _L
1 ms
OPEN
CLOSE
Gate time 4 ms
8 ms
Count period (IFCG flag = 1)
Gate is actually opened at this point
IFCSTRT flag is set
IFCG flag is set at this point
End of counting
IFG flag is cleared
(2) When gate is open
If opening of the gate is selected by the IFCCK1 and IFCCK0 flags, the gate is opened as soon as its opening
has been selected, as illustrated below.
If the counter is started by using the IFCSTRT flag while the gate is open, the gate is closed after an undefined
amount of time.
To open the gate, therefore, do not set the IFCSTRT flag to 1.
However, the counter can be reset by the IFCRES flag.
H
Internal 1 kHz _L
Gate
OPEN
CLOSE
Count period
Gate is closed after an undefined amount of time if IFCSTRT flag is set
during this period
Sets IFCCK1 = IFCCK0 = 1
Gate is actually opened at this point.
If gate is opened while IFCG flag is 1, it is closed after an undefined amount of time
The gate is opened or closed in the following two ways when opening the gate is selected as the gate time.
Data Sheet U10101EJ4V0DS
203