UPD17073 NEC, UPD17073 Datasheet - Page 150

• Manufacturer Part Number: UPD17073
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER WITH HARDWARE FOR DIGITAL TUNING SYSTEM
• Manufacturer: NEC

16.3.2
150
Internal 1 kHz
Gate
(1) When gate time is set to 1, 4, or 8 ms
1 ms
4 ms
8 ms
(2) When gate time is open
Internal 1 kHz
Gate
As shown below, the gate is opened for 1, 4, or 8 ms starting from the rising edge of an internal 1-kHz signal
after the IFCSTRT flag has been set.
While the gate is open, the frequency of a signal input to a specific pin is counted by a 16-bit counter.
When the gate is closed, the IFCG flag is cleared (0).
The IFCG flag is automatically set to “1” as soon as the IFCSTRT flag has been set.
When the gate time is specified by the IFCCK1 and IFCCK0 flags to be open, the gate is immediately opened.
If counting is started by the IFCSTRT flag while the gate is open, the gate is closed after an undefined time.
Therefore, do not set the IFCSTRT flag to “1” when the gate time is open.
However, the counter can be reset by the IFCRES flag.
When the gate time is open, the gate can be opened and closed by resetting the gate time other than open
by using IFCCK1 and IFCCK0 flags.
Gate operation of IF counter function
CLOSE
CLOSE
CLOSE
OPEN
OPEN
OPEN
H
H
L
L
Sets IFCCK1 = IFCCK0 = 1
Sets IFCCK1 = IFCCK0 = 1
Gate is actually opened at this point.
If gate is opened with IFCG flag set to 1, it is closed after undefined time
IFCSTRT flag is set
(IFCG flag is set by the instruction after IFCSTRT flag is set)
Count period
If IFCSTRT flag is set during this period, gate is closed after undefined time
Actual gate open at this point
Count period
Count period (IFCG flag = 1)
Other than open is set by IFCCK1 and
IFCCK0 flags
PD17072,17073
Count ends
IFCG flag is cleared