SN8A1702AX datasheet(75/112 Pages) SONIX

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Preliminary

SN8P1702A/SN8P1703A

8-bit micro-controller build-in 12-bit ADC

SONiX TECHNOLOGY CO., LTD

Page 75

Revision 0.5

PWM FUNCTION DESCRIPTION

OVERVIEW

PWM function is generated by TC0/TC1 timer counter and output the PWM signal to PWM0OUT pin (P5.4)/

PWM1OUT pin (P5.3). When code option TC0/TC1_Counter= 8-bit, the counter counts modulus 256, from 0-255,

inclusive. The value of the 8-bit counter is compared to the contents of the reference register (TC0R/TC1R). When the

reference register value (TC0R/TC1R) is equal to the counter value (TC0C/TC1C), the PWM output goes low. When

the counter reaches zero, the PWM output is forced high. Following table listed the low-to-high ratio (duty) of the

PWM0/PWM1 output.

For example, TC0_Counter=8-bit, all PWM outputs remain inactive during the first 256 input clock signals. Then, when

the counter value (TC0C/TC1C) changes from FFH back to 00H, the PWM output is forced to high level. The pulse

width ratio (duty cycle) is defined by the contents of the reference register (TC0R/TC1R) and is programmed in

increments of 1:256. The 8-bit PWM data register TC0R/TC1R is write-only register. Different code option of

TC0_Counter/TC1_Counter will cause different PWM Duty, so user can generate different PWM output by selection

different TC0_Counter/TC1_Counter.

PWM output can be held at low level by continuously loading the reference register with 00H. Under PWM operating, to

change the PWM’s duty cycle is to modify the TC0R/TC1R.

TC0X8/TC1X8

PWM0 Frequency

PWM1 Frequency

Fosc/(2

10-TC0RATE)/N

Fosc/(2

10-TC1RATE)/N

Fosc/(2

7-TC0RATE) /N

Fosc/(2

7-TC1RATE) /N

The value of N depend on code option TC0_Counter/TC1_Counter

TC0_Counter/TC1_Counter

PWM Duty Cycle

8-bit

256

0/256 ~ 255/256

6-bit

0/64 ~ 63/64

5-bit

0/32 ~ 31/32

4-bit

0/16 ~ 15/16

Table 8-6. The PWM Frequency Calculation Formula

TC0X8

TC1X8

TC0_Counter

TC1_Counter

TC0 Overflow

boundary

TC1 Overflow

boundary

PWM Duty Cycle

Max PWM Frequency

(Fosc = 4MHz)

Note

8-bit

FFh to 00h

0/256 ~ 255/256

1.953125K

Overflow per 256 count

6-bit

3Fh to 40h

0/64 ~ 63/64

7.8125K

Overflow per 64 count

5-bit

1Fh to 20h

0/32 ~ 31/32

15.625K

Overflow per 32 count

4-bit

0Fh to 10h

0/16 ~ 15/16

31.25K

Overflow per 16 count

8-bit

FFh to 00h

0/256 ~ 255/256

15.625

Overflow per 256 count

6-bit

3Fh to 40h

0/64 ~ 63/64

62.5K

Overflow per 64 count

5-bit

1Fh to 20h

0/32 ~ 31/32

125K

Overflow per 32 count

4-bit

0Fh to 10h

0/16 ~ 15/16

250K

Overflow per 16 count

Table 8-7. The Maximum PWM Frequency Example (TC0RATE/TC1RATE = 111)

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