Samsung S3F84A5 - Manual (Page 14)

S3F84P4_AN_REV0.00 (PRELIMINARY SPEC) 3 SOFTWARE IMPLEMENTATION
N
Y
Decrease PWM duty cycle
Start
PWMEX>=100B?
PWMEX = 0xFF
PWMDATA - =1
End
PWMEX - =1
N
Y
Increase PWM duty cycle
Start
PWMEX>=
11111100B?
PWMEX + = 1
End
PWMEX = 0
PWMDATA + =1
Figure 3-2 Way to change PWM duty cycle
 Change rate of PWM duty cycle: If PWM in S3F84P4 is 6+6 type, the PWM basic frequency is 6-bit, that
is,
6
8
125
2 64
PWM
f MHz
KHz
 
8
PWM
f MHz

when . The overall cycle is still 12-bit to make the 12-bit
resolution fully valid, that is,
12 2
PWM
ms
4096
0.512
8 f MHz
 
. So Therefore, every change of the duty cycle will
take effect after 0.512ms. Considering the AD conversion duration is 25us, duty cycle can be updated every
21 times of AD conversion.
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