M38504M6-200FP Ver la hoja de datos (PDF) - MITSUBISHI ELECTRIC
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M38504M6-200FP Datasheet PDF : 86 Pages
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MITSUBISHI MICROCOMPUTERS
3850 Group (Spec. H)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
PULSE WIDTH MODULATION (PWM)
The 3850 group (spec. H) has a PWM function with an 8-bit
resolution, based on a signal that is the clock input XIN or that
clock input divided by 2.
Data Setting
The PWM output pin also functions as port P44. Set the PWM
period by the PWM prescaler, and set the “H” term of output pulse
by the PWM register.
If the value in the PWM prescaler is n and the value in the PWM
register is m (where n = 0 to 255 and m = 0 to 255) :
PWM period = 255 ✕ (n+1) / f(XIN)
= 31.875 ✕ (n+1) µs
(when f(XIN) = 8 MHz,count source selection bit = “0”)
Output pulse “H” term = PWM period ✕ m / 255
= 0.125 ✕ (n+1) ✕ m µs
(when f(XIN) = 8 MHz,count source selection bit = “0”)
PWM Operation
When bit 0 (PWM enable bit) of the PWM control register is set to
“1”, operation starts by initializing the PWM output circuit, and
pulses are output starting at an “H”.
If the PWM register or PWM prescaler is updated during PWM
output, the pulses will change in the cycle after the one in which
the change was made.
31.875 ✕ m ✕ (n+1) µs
255
PWM output
T = [31.875 ✕ (n+1)] µs
m: Contents of PWM register
n : Contents of PWM prescaler
T : PWM period (when f(XIN) = 8 MHz,count source
selection bit = “0”)
Fig. 27 Timing of PWM period
Data bus
PWM
prescaler pre-latch
PWM
register pre-latch
Transfer control circuit
XIN
(XCIN at low-speed mode)
PWM
prescaler latch
Count source
selection bit
“0”
PWM prescaler
1/2 “1”
PWM
register latch
PWM register
Port P44
Port P44 latch
PWM enable bit
Fig. 28 Block diagram of PWM function
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