68HC11 Timing System

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The Free-Running Counter ELET 3144 R. Alba-Flores 6
The Prescalar • Resolution is the smallest time interval that can be measured in a system. • In the <strong>68HC11</strong> the TCNT register is incremented once every 0.5 µsec. This 0.5 µsec is the resolution of the microcontroller system. • Because the TCNT register is 16 bits, it takes 65,536 ( 2 16 ) counts to cycle it around once. • At the standard clock frequency of 2 MHz, the TCNT register requires 32.77 msec to roll over ( 65,536 x 0.5 µsec). ELET 3144 R. Alba-Flores 7
Page 1 and 2: 68HC11 Timing System ELET 3144 R. A
Page 3 and 4: Time Measuring Methods There are di
Page 5: The Free-Running Counter • The ou
Page 9 and 10: Timer Overflow Every time the TCNT
Page 11 and 12: Example 1 • The TCNT register can
Page 13 and 14: ; * Subroutine to clear TOF SUB2: L
Page 15 and 16: Input Capture Registers Input captu
Page 17 and 18: The three 16-bit TIC registers (TIC
Page 19 and 20: Example 3. The time of a falling ed
Page 21 and 22: The corresponding interrupt bit is
Page 23 and 24: ; *** This is a program to determin

68HC11 Timing System

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