m3819 Renesas Electronics Corporation., m3819 Datasheet - Page 97

• Manufacturer Part Number: m3819
• Description: Mitsubishi 8-bit Single-chip Microcomputer 740 Family / 38000 Series
• Manufacturer: Renesas Electronics Corporation.

2. APPLICATION
Fig 2.2.19 A method for judging if Video synchronization signal exists
(4) Timer application example 3 : Measurement of frequency
Figure 2.2.19 shows a method for judging if Video synchronization signal exists, and Figure 2.2.20 shows a setting
of related registers.
Outline : The pulses input to the External count input pin (CNTR) are counted by a timer to judge if the
Specifications : • The Video synchronization signal is input to the CNTR
Video synchronization signal
frequency is within a certain range.
• A count value is read out at the interval of about 2 ms (Timer 1 interrupt interval : 244 s
• Because the timer is a down-counter, the count value is compared with 227 to 215.
8). When the count value is 28 to 40, it is regarded as the existence of the Video synchro-
nization signal.
*
227 to 215 = 255 (initialized value of counter) – 28 to 40 (the number of valid value).
(judging if Video synchronization signal exists)
3819 Group USER’S MANUAL
(15.7 kHz)
63.5 s
244 s
63.5 s
1
pin and counted by the Timer 4.
8
MITSUBISHI MICROCOMPUTER
= 31 counts
3819 Group
2.2 Timer
*
83