MC68HC708MP16CFU Pwm Generators - Freescale Semiconductor, Inc

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MC68HC708MP16CFU

Manufacturer Part Number
MC68HC708MP16CFU
Description
Manufacturer
Freescale Semiconductor, Inc
Datasheet
9.4.2 Prescaler
To permit lower PWM frequencies, a prescaler is provided which will
divide the PWM clock frequency by 1, 2, 4, or 8.
setting the prescaler bits in PWM control register 2 affects the PWM
clock frequency. This prescaler is buffered and will not be used by the
PWM generator until the LDOK bit is set and a new PWM reload-cycle
begins.
9.5 PWM Generators
Pulse width modulator (PWM) generators are discussed in the following
subsections.
9.5.1 Load Operation
To help avoid erroneous pulse widths and PWM periods, the modulus,
prescaler, and PWM value registers are buffered. New PWM values,
counter modulus values, and prescalers can be loaded from their buffers
into the PWM module every one, two, four, or eight PWM cycles.
LDFQ1:LDFQ0 in PWM control register 2 are used to control this reload
frequency, as shown in
regardless of whether an actual reload occurs (as determined by the
LDOK bit), the PWM reload flag bit in PWM control register 1 will be set.
If the PWMINT bit in PWM control register 1 is set, a CPU interrupt
request will be generated when PWMF is set. Software can use this
interrupt to calculate new PWM parameters in real time for the PWM
module.
MC68HC708MP16
Rev. 3.1
Freescale Semiconductor
Pulse Width Modulator for Motor Control (PWMMC)
Pulse Width Modulator for Motor Control (PWMMC)
Table 9-1. PWM Prescaler
Prescaler Bits
PWM Clock Frequency
PRSC1:PRSC0
00
01
10
11
Table
9-2. When a reload cycle arrives,
Table 9-1
shows how
f
op
f
/2
op
f
/4
op
f
/8
op
Technical Data
137

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