7721 datasheet(159/577 Pages) RENESAS

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TIMER A

7721 Group User’s Manual

8–40

8.6 Pulse width modulation (PWM) mode

8.6.1 Setting for PWM mode

Figures 8.6.2 and 8.6.3 show an initial setting example for registers relevant to the PWM mode.

Note that when using interrupts, set up to enable the interrupts. For details, refer to

“CHAPTER 7.

INTERRUPTS.”

Fig. 8.6.2 Initial setting example for registers relevant to PWM mode (1)

Note: When operating as 8-bit pulse width modulator

fi : Frequency of count source

However, if n = “0016”, the pulse width modulator

does not operate and the TAjOUT pin outputs “L”

level. At this time, no timer Aj interrupt request

occurs.

Count source select bits

0 0 : f2

0 1 : f16

1 0 : f64

1 1 : f512

Selecting PWM mode and each function

Timer Aj mode register (j = 2 to 4) (Addresses 5816 to 5A16)

b7 b6

16/8-bit PWM mode select bit

0 : Operates as 16-bit pulse width modulator

1 : Operates as 8-bit pulse width modulator

Continue to Figure 8.6.3.

Trigger select bits

0 0 :

0 1 :

1 0 : Falling edge of TAjIN pin’s input signal

1 1 : Rising edge of TAjIN pin’s input signal

Selection of PWM mode

Setting PWM pulse’s period and “H” level width

Can be set to “000016” to “FFFE16” (n)

(b15)

(b8)

Timer A2 register (Addresses 4B16, 4A16)

Timer A3 register (Addresses 4D16, 4C16)

Timer A4 register (Addresses 4F16, 4E16)

Note: When operating as 16-bit pulse width modulator

fi : Frequency of count source

However, if n = “000016”, the pulse width modulator does

not operate and the TAjOUT pin outputs “L” level. At this time,

no timer Aj interrupt request occurs.

q When operating as 16-bit pulse width modulator

Can be set to “0016” to “FF16” (m)

(b15)

(b8)

q When operating as 8-bit pulse width modulator

Can be set to “0016” to “FE16” (n)

Timer A2 register (Addresses 4B16, 4A16)

Timer A3 register (Addresses 4D16, 4C16)

Timer A4 register (Addresses 4F16, 4E16)

Writing “1” to count start bit: Internal trigger

: External trigger

“H” level width =

Period =

“H” level width =

Period =

216 – 1

(m+1) (28 –1 )

n(m+1)

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