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M66242P

4-CH 12-BIT PWM GENERATOR

MITSUBISHI ELECTRIC  

MITSUBISHI 〈DIGITAL ASSP〉

M66242P/FP

4-CH 12-BIT PWM GENERATOR

FUNCTION

The PWM output waveform of each channel is controlled by

taking in PWM data from MCU or other device via serial data

input SIN.

Twelve-bit PWM data is input being divided between upper 8

bits (upper byte) and lower 4 bits.

The lower 4-bit data is combined with command data such as

channel designation and input as 8-bit data (lower byte).

The lower byte should be written first, and then the upper

byte. Even if only the upper byte is to be changed, rewrite

from the lower byte.

The PWM waveform changes according to the new setting

from the next cycle.

One cycle of PWM waveform (4096 divisions; 12-bit resolu-

tion) are divided into 16 (24) subsections t. Each subsection

consists of 256 (28; 8-bit resolution) minimum bits τ (=2/

fXIN**).

One subsection t consists of a 8-bit PWM waveform (basic

waveform). The “H” width of this waveform is determined ac-

cording to the upper 8 bits of PWM data. One cycle has 16

subsections t, each of which has this basic waveform. Among

them, those which are designated by the 4-bit-rate multiplier

are conditioned to have a “H” width that is longer by τ. The

lower 4 bits of PWM data are used to specify those subsec-

tions (tm). The waveform of other subsections remains un-

changed.

A PWM waveform (12-bit resolution) is a combination of two

types of waveforms which are different in “H” width, as de-

scribed above.

When output control input OC is “H”, the output of every

channel turns high-impedance from the next cycle.

When reset input R is “L”, the output of every channel turns

high-impedance as soon as the ongoing cycle is completed,

and PWM data of all channels is reset. If R input is changed

from “L” to “H”, the next cycle starts, however, the output of

the channels remains high-impedance.

To enable output, rewrite input data for each channel.

**)fXIN: Clock XIN repeat frequency

PIN DESCRIPTIONS

Pin

Name

R

Reset input

CS

Chip select input

WR

SIN

SCLK

OC

PWM1~PWM4

Write control input

Serial data input

Write clock input

Output control input

PWM outputs 1 thru 4

XIN

Clock input

XOUT

Clock output

Input/Output

Input

Input

Input

Input

Input

Input

Output

Input

Output

Functions

“L”: All 4 channels put in high impedance state.

“L”: Communication with MCU becomes possible. WR, SIN and SCLK put in

enable state.

“L”: Serial data written.

“L”-to-“H” edge: Written data stored in upper or lower byte.

Inputs 8-bit serial data from MCU synchronously with clock pulses.

Inputs sync clock pulses for 8-bit serial data writing.

“H”: All 4 channels put in high-impedance state.

Outputs PWM waveform. (CMOS 3-state output)

Inputs/outputs signals generated by clock signal generation circuit. Oscillation

frequency is determined by connecting ceramic or quartz resonator between

XIN and XOUT. The frequency of internal clock (PWM timing clock) signals is

the 1/2 divider of the frequency input from clock input XIN. When external

clock signals are used, connect clock generator to XIN pin and leave XOUT

open.

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