PFS172 datasheet(45/92 Pages) PADAUK

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PFS172

8bit MTP MCU with 8-bit ADC

Page 45 of 92

PDK-DS-PFS172-EN_V000-May 8, 2020

5.7.2

Using the Timer2 to generate 8-bit PWM waveform

If 8-bit PWM mode is selected, it should set tm2c[1]=1 and tm2s[7]=0, the frequency and duty cycle of

output waveform can be summarized as below:

Frequency of Output = Y ÷ [256 × S1 × (S2+1) ]

Duty of Output = [( K＋1 ) ÷ 256]×100%

Where,

Y = tm2c[7:4] : frequency of selected clock source

K = tm2b[7:0] : bound register in decimal

S1= tm2s[6:5] : pre-scalar (S1= 1, 4, 16, 64)

S2 = tm2s[4:0] : scalar register in decimal (S2= 0 ~ 31)

Example 1:

tm2c = 0b0001_1010, Y=8MHz

tm2b = 0b0111_1111, K=127

tm2s = 0b0_00_00000, S1=1, S2=0

 frequency of output = 8MHz ÷ ( 256 × 1 × (0+1) ) = 31.25KHz

 duty of output = [(127+1) ÷ 256] × 100% = 50%

Example 2:

tm2c = 0b0001_1010, Y=8MHz

tm2b = 0b0111_1111, K=127

tm2s = 0b0_11_11111, S1=64, S2=31

 frequency of output = 8MHz ÷ ( 256 × 64 × (31+1) ) = 15.25Hz

 duty of output = [(127+1) ÷ 256] × 100% = 50%

Example 3:

tm2c = 0b0001_1010, Y=8MHz

tm2b = 0b1111_1111, K=255

tm2s = 0b0_00_00000, S1=1, S2=0

 PWM output keep high

 duty of output = [(255+1) ÷ 256] × 100% = 100%

Example 4:

tm2c = 0b0001_1010, Y=8MHz

tm2b = 0b0000_1001, K = 9

tm2s = 0b0_00_00000, S1=1, S2=0

 frequency of output = 8MHz ÷ ( 256 × 1 × (0+1) ) = 31.25KHz

 duty of output = [(9+1) ÷ 256] × 100% = 3.9%

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