Chapter 4 Timer Functions

4-3 16-bit Timer Operation (timer 4)

4-3-1 Overview

Timer 4 is a 16-bit programmable counter that can be used as an event counter.

A signal with a frequency of 1/2 of the timer 4 overflow signal can be output from the TM4IO pin. An input capture function and pulse added type PWM output function can also be used.

4-3-2 Operation

Timer Operation

Settings for timer operation are listed below.

(1)Set the TM4EN flag of the timer 4 mode register (TM4MD) to "0" to stop the count operation of timer 4.

(2)Set the TM4CK2 to 0 flags of the TM4MD register to select fosc, fs/4, or fs/16 as the clock source.

(3)Set the TM4PWM flag of the TM4MD register to "0" to select 16-bit timer operation.

(4)Set a value in compare register 4 (TM4OCH, TM4OCL).

(5)Set the TM4EN flag of the TM4MD register to "1" to start the timer.

(6)When timer 4 begins operation, binary counter 4 counts upward from X'0000'.

(7)When the value of binary counter 4 matches that of the TM4OCH and TM4OCL registers, the timer 4 interrupt request flag is set, the value of binary counter 4 is reset to X'0000', and counting begins again.

When servicing an interrupt, reset the timer 4 interrupt request flag before operating timer 4.

During a count operation, be careful if the value set in TM4OCH and TM4OCL is smaller than the value of binary counter 4, since the count-up operation will continue until overflow occurs.

16-bit Timer Operation (timer 4)

69

Page 83
Image 83
Panasonic MN101C00 user manual bit Timer Operation timer, Overview