M66242P データシートの表示（PDF） - Mitsumi

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M66242P

4-CH 12-BIT PWM GENERATOR

Mitsumi 

MITSUBISHI 〈DIGITAL ASSP〉

M66242P/FP

4-CH 12-BIT PWM GENERATOR

Upper byte register

b7

b0

01001010

Lower byte register

b7

b0

0110????

PWM register

b11

b4 b3

b0

4A616 0 1 0 0 1 0 1 0 0 1 1 0

Determines “H” width of basic waveform

(In this case, “H” width is 4A16 = 74)

Basic waveform τ × 74

Determines subsections tm whose

“H” width is increased by

the minimum bit width of τ

(Refer to Table 2.)

(In this case, m = 2, 4, 6, 10, 12 and 14.)

τ × 74

τ

τ=

2

fXIN

(e.g. When fXIN is 4 MHz, τ = 0.5µs)

Output waveform

One subsection

t = τ × 256

(8-bit resolution)

τ × 74

τ τ × 74

Designated subsection

tm

(In this case, m = 2, 4, 6, 10, 12 and 14.)

τ × 75

t0

t4

t5

t6

t7

t8

t9

t10

t11

t12

t13

t15

Subsection

One cycle

Fig. 2 PWM Waveform Output Example (Input data: 4A6 16)

OPERATION

Serial Data Input

When chip select CS is “L” and write control input WR is “L”,

data input to SIN at the edge where write clock input SCLK sta-

tus shifts from “L” to “H” is written. (See Fig. 3.)

At the edge where WR rises from “L” to “H”, the latest 8-bit

data writing is completed, and input data is stored in lower (or

upper) byte register. When writing on the lower byte or writing

on both upper and lower bytes is completed, data on the

lower byte register or, in the latter case, data on both lower

and upper byte registers is written on the PWM register of the

channel designated by lower bytes b2 and b1. All setting pro-

cess ends with this writing, and PWM waveform changes ac-

cording to the setting from the next cycle.

PWM Waveform Output

(1) 12-bit PWM output

One PWM waveform cycle is divided into 16(24) subsec-

tions t, and each subsection is further divided into 256 (28)

minimum resolution bits τ (= 2/fXIN)

The “H” width of subsection t basic waveform is deter-

mined by the upper 8 bits of PWM data.

(In Fig. 2 above, “H” width is 4A16 = 74 × τ)

Among these 16 subsections t, subsections tm designated

by the lower 4 bits of PWM data have “H” width that is

longer by τ.

[In Fig. 2 above, the “H” width of designated 6 subsections

(m =2, 4, 6, 10, 12 and 14) is 4B16 = 75 × τ.]

4

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