Intel PXA255 - Manual (Page 147)

Intel® PXA255 Processor Developer’s Manual 4-43
System Integration Unit
4.5.3 Pulse Width Modulator Output Wave Example
Figure 4-4 is an example of the output of a Pulse Width Modulator for reference.
PWM_PERVAL[PV] = 0xA
PWM_DUTY[FDCYCLE] = 0x0
PWM_DUTY[DCYCLE] = 0x6
PWM_CTRL[PRESCALE] = 0x0
The output waveform in Figure 4-4 is created by writing PWM_PERVALn[PV] with a decimal
value of 10 (11 clocks) and PWM_DUTYn[DCYCLE] with 6. Figure 4-4 also shows that
PWM_CTRLn[PRESCALE] is configured with a value of 0x0 loaded, which results in the
PSCLK_PWMn having the same frequency as the 3.6864 MHz input clock.
Table 4-48. PWM_PERVALn Bit Definitions
Physical Address
0x40B0_0008
0x40C0_0008
PWM Period Control Registers
(PWM_PERVAL0, PWM_PERVAL1)
System Integration Unit
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved PV
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
Bits Name Description
<31:10> — reserved
<9:0> PV
PWMn Period Control:
The number of PSCLK_PWMn cycles that comprise one PWM_OUTn cycle
NOTE: If PV = 0x0, the PWMn clock (PWM_OUTn) is set high and does not toggle unless
FDCYCLE=0x0 and DCYCLE=0x0. In this case PWM_OUTn is set low and does
not toggle regardless of the value in PV.
Figure 4-4. Basic Pulse Width Waveform
PWM_OUTn
PSCLK_PWMn
PWM_DUTYn = 6
PWM_PERVALn = 10 (+1)
3.6864 MHz