SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
8.5 PWMn MODE
8.5.1 OVERVIEW
PWM function is generated by TCn timer counter and output the PWM signal to PWM0OUT pin (P5.3), PWM1OUT pin
(P5.4) PWM2OUT pin (P5.5). The 8-bit counter counts modulus 256, 64, 32, 16 controlled by ALOADn, TCnOUT bits.
The value of the 8-bit counter (TCnC) is compared to the contents of the reference register (TCnR). When the
reference register value (TCnR) is equal to the counter value (TCnC), the PWM output goes low. When the counter
reaches zero, the PWM output is forced high. The low-to-high ratio (duty) of the PWMn output is TCnR/256, 64, 32, 16.
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 TCnR.
Note: TCn is double buffer design. Modifying TCnR to change PWM duty by program, there is no glitch
and error duty signal in PWM output waveform. Users can change TCnR any time, and the new reload
value is loaded to TCnR buffer at TCn overflow.
MAX. PWM
ALOADn TCnOUT PWM duty range TCnC valid value TCnR valid bits value
Frequency
(Fcpu = 6MHz)
11.719K
Remark
0
0
1
1
0
1
0
1
0/256~255/256
0/64~63/64
0/32~31/32
0/16~15/16
0x00~0xFF
0x00~0x3F
0x00~0x1F
0x00~0x0F
0x00~0xFF
0x00~0x3F
0x00~0x1F
0x00~0x0F
Overflow per 256 count
Overflow per 64 count
Overflow per 32 count
Overflow per 16 count
46.875K
93.75K
187.5K
The Output duty of PWM is with different TCnR. Duty range is from 0/256~255/256.
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