M38005M2DXXXFP View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

Manufacturer

M38005M2DXXXFP

8-BIT SINGLE-CHIP MICROCOMPUTER

MITSUBISHI ELECTRIC  

APPLICATION

2.2 Timer

(4) Timer application example 3 : Measurement of frequency

Outline : The following two values are compared for judging if the frequency is within a certain range.

• A value counted a pulse which is input to P55/CNTR1 pin by a timer.

• A referance value

Specifications : • The pulse is input to the P55/CNTR1 pin and counted by the Timer Y.

• A count value is read out at the interval of about 2 ms (Timer 1 interrupt interval

: 244 µs ! 8). When the count value is 28 to 40, it is regarded the input pulse

as a valid.

• Because the timer is a down-counter, the count value is compared with 227 to 215V .

V 227 to 215 = 255 (initialized value of counter) – 28 to 40 (the number of valid

value).

Figure 2.2.17 shows a method for judging if input pulse exists, and Figure 2.2.18 shows a setting of

related registers.

Input pulse

••••

••••

••••

71.4 µs or more

(14 kHz or less)

Invalid

71.4 µs

(14 kHz)

Valid

50 µs(20 kHz)

50 µs or less

(20 kHz or more)

Invalid

2 ms

71.4 µs

= 28 counts

2 ms

50 µs

= 40 counts

Fig 2.2.17 A method for judging if input pulse exists

3800 GROUP USER’S MANUAL

2-17

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