NEC mPD789426 Series, User Manual

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CHAPTER 7 8-BIT TIMER
User’s Manual U15075EJ1V0UM00
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(2) Operation as external event counter with 8-bit resolution (timer 60 only)
The external event counter counts the number of external clock pulses input to the TMI60/P31/INTP1/TO50
pin by using 8-bit timer counter 60 (TM60).
To operate timer 60 as an external event counter, settings must be made in the following sequence.
<1> Disable operation of 8-bit timer counter 60 (TM60) (TCE60 = 0).
<2> Disable timer output of TO60 (TOE60 = 0).
<3> Set P31 to input mode (PM31 = 1).
<4> Select the external input clock for timer 60 (see Table 7-5).
<5> Set the operation mode of timer 60 to 8-bit timer counter mode (see Figures 7-4 and 7-5).
<6> Set a count value in CR60.
<7> Enable the operation of TM60 (TCE60 = 1).
Each time the valid edge is input, the value of TM60 is incremented.
When the count value of TM60 matches the value set in CR60, TM60 is cleared to 00H and continues
counting. At the same time, an interrupt request signal (INTTM60) is generated.
Figure 7-14 shows the timing of the external event counter operation.
Caution Be sure to stop the timer operation before overwriting the count clock with different data.