7513 datasheet(35/66 Pages) RENESAS

35 / 66 page

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

7513 Group

PULSE WIDTH MODULATION (PWM)

The 7513 group has a PWM function with an 8-bit resolution,

based on a signal that is the clock input XIN or that clock input di-

vided by 2.

Data Setting

The PWM output pin also functions as ports P50 and P51. Set the

PWM period by the PWM prescaler, and set the period during

which the output pulse is an “H” by the PWM register.

If PWM count source is f(XIN) and 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)

= 51 ✕ (n+1)

µs (when f(XIN) = 5 MHz)

Output pulse “H” period = PWM period ✕ m/255

= 0.2 ✕ (n+1) ✕ m

µs

(when f(XIN) = 5 MHz)

PWM Operation

When at least either bit 1 (PWM0 output enable bit) or bit 2 (PWM1

output enable bit) of the PWM control register is set to “1”, opera-

tion starts by initializing the PWM output circuit, and pulses are

output starting at an “H”. When one PWM output is enabled and

that the other PWM output is enabled, PWM output which is en-

abled to output later starts pulse output from halfway.

When 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.

Fig. 31 Timing of PWM cycle

Fig. 32 Block diagram of PWM function

51 ✕ m ✕ (n+1)

255

µs

T = [51 ✕ (n+1)]

µs

PWM output

m: Contents of PWM register

n : Contents of PWM prescaler

T : PWM cycle (when f(XIN) = 5 MHz)

Data bus

Count source

selection bit

“0”

“1”

PWM

prescaler pre-latch

PWM

prescaler latch

PWM

Transfer control circuit

PWM circuit

1/2

XIN

PWM0 enable bit

Port P51

PWM prescaler

PWM1 enable bit

Port P50

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