M37516M6-A05 データシートの表示（PDF） - Mitsumi

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M37516M6-A05

Single chip 8-bit microcomputer

Mitsumi 

PULSE WIDTH MODULATION (PWM)

The M37516M6-XXXHP has a PWM function with an 8-bit resolu-

tion, 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 pe-

riod 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) us

(when f(XIN) = 8 MHz, count source is f(XIN) )

Output pulse “H” term = PWM period ! m / 255

= 0.125 ! (n+1) ! m us

(when f(XIN) = 8 MHz, count source is f(XIN))

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) us

255

PWM output

T = [31.875 ! (n+1)] us

m: Contents of PWM register

n : Contents of PWM prescaler

T : PWM period (when f(XIN) = 8 MHz,

count source is f(XIN))

Fig. 36 Timing of PWM period

Data bus

PWM

prescaler pre-latch

PWM

register pre-latch

Transfer control circuit

PWM

prescaler latch

Count source

selection bit

XIN

“0”

PWM prescaler

1/2 “1”

PWM

register latch

PWM register

Fig. 37 Block diagram of PWM function

Port P44

Port P44 latch

PWM enable bit

M37516M6-XXXHP

GNOK-M37516M6-XXXHP-50

(MSETSU 2)

PA

GE

35/54

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