MC9S12HY64 Datasheet, PDF (709/792 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Motor Controller (MC10B8CV1)
19.4.2 PWM Duty Cycle
The PWM duty cycle for the motor controller channel x can be determined by dividing the decimal
representation of bits D[10:0] in MCDCx by the decimal representation of the bits P[10:0] in MCPER and
multiplying the result by 100% as shown in the equation below:
Effective PWM Channel X % Duty Cycle = _M---^D---_C-^U----_P-^T--_E--^Y--_R--- ⋅ 100%
NOTE
x = PWM Channel Number = 0, 1, 2, 3 ... 8. This equation is only valid if
DUTY <= MCPER and MCPER is not equal to 0.
Whenever D[10:0] >= P[10:0], a constant low level (RECIRC = 0) or high level (RECIRC = 1) will be
output.
19.4.3 Motor Controller Counter Clock Source
Figure 19-22 shows how the PWM motor controller timer counter clock source is selected.
Clock
Generator
CLK
Peripheral
Bus
Clock f_BUS
Clocks and
Reset
Generator
Module
Motor Controller
Timer
Counter Clock
Prescaler Select
MPPRE0, MPPRE1
1
1/2
Motor Controller Timer
1/4
1/8
Counter Clock f_TC
Motor Controller Timer
Counter Prescaler
11-Bit Motor Controller
Timer Counter
Figure 19-22. Motor Controller Counter Clock Selection
The peripheral bus clock is the source for the motor controller counter prescaler. The motor controller
counter clock rate, f_TC, is set by selecting the appropriate prescaler value. The prescaler is selected with
the MCPRE[1:0] bits in motor controller control register 0 (MCCTL0). The motor controller channel
frequency of operation can be calculated using the following formula if DITH = 0:
Motor Channel Frequency (Hz) = _M------_C-----_P--^f-_E-^T--^C-_R------_â‹---_M----
MC9S12HY/HA-Family Reference Manual, Rev. 1.04
Freescale Semiconductor
709