Event Count Function

Settings for the event count function 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)Use the TM4CK2 to 0 flags of the TM4MD register to select TM4IO input or synchronized TM4IO input as the clock source.

(3)Set the TM4PWM flag of the TM4MD register to "0" so that 16-bit timer operation is selected.

(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 will count 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, and the binary counter 4 is reset to X'0000' and begins to count upward again.

When synchronized TM4IO is selected, the timer 4 clock source is synchronized with the system clock after a transition of the TM4IO input signal. Timer 4 counts upward based on a signal synchronized to the system clock. Therefore, correct values can be read from binary counter 4.

Figure 4-3-2 Timer 4 Event Counter Timing (when synchronous TM4IO

CPU system clock (fs)

TM4IO input

Synchronous circuit output

Binary counter

n

n+1

input is selected)

Chapter 4 Timer Functions

If TM4IO input is selected as the clock source and the value of binary counter 4 is to be read during operation, select synchronized TM4IO input to avoid reading data that may be incomplete during count-up transitions. However, with synchronized TM4IO input, it is not possible to return from STOP/HALT modes.

16-bit Timer Operation (timer 4)

71

Page 85
Image 85
Panasonic MN101C00 user manual Timer Functions