M37271MF-252SP datasheet(22/97 Pages) MITSUBISHI

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MITSUBISHI MICROCOMPUTERS

M37271MF-XXXSP

M37271EF-XXXSP, M37271EFSP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER

and ON-SCREEN DISPLAY CONTROLLER

PWM OUTPUT FUNCTION

The M37271MF-XXXSP is equipped with seven 8-bit PWMs (PWM0–

PWM6). PWM0–PWM6 have the same circuit structure and an 8-bit

resolution with minimum resolution bit width of 4

µs (for f(XIN) = 8

MHz) and repeat period of 1024

µs.

Figure 15 shows the PWM block diagram. The PWM timing generat-

ing circuit applies individual control signals to PWM0–PWM6 using

f(XIN) divided by 2 as a reference signal.

(1) Data Setting

When outputting PWM0–PWM6, set 8-bit output data in the PWMi

(2) Transmitting Data from Register to PWM circuit

Data transfer from the 8-bit PWM register to 8-bit PWM circuit is

executed at writing data to the register.

The signal output from the 8-bit PWM output pin corresponds to the

contents of this register.

(3) Operating of 8-bit PWM

The following is the explanation about PWM operation.

At first, set the bit 0 of PWM mode register 1 (address 020A16) to “0”

(at reset, bit 0 is already set to “0” automatically), so that the PWM

count source is supplied.

PWM0–PWM3 are also used as pins P04–P07, PWM4–PWM6 are

also used as pins P00–P02, respectively. Set the corresponding bits

of the port P0 direction register to “1” (output mode). And select each

output polarity by bit 3 of the PWM mode register 1 (address 020A16).

Then, set bits 7 to 0 of the PWM output control register 2 to “1”

(PWM output).

The PWM waveform is output from the PWM output pins by setting

these registers.

Figure 16 shows the 8-bit PWM timing. One cycle (T) is composed

of 256 (28) segments. The 8 kinds of pulses relative to the weight of

each bit (bits 0 to 7) are output inside the circuit during 1 cycle. Refer

to Figure 16 (a). The 8-bit PWM outputs waveform which is the logi-

cal sum (OR) of pulses corresponding to the contents of bits 0 to 7 of

the 8-bit PWM register. Several examples are shown in Figure 16

(b). 256 kinds of output (“H” level area: 0/256 to 255/256) are se-

lected by changing the contents of the PWM register. A length of

entirely “H” output cannot be output, i.e. 256/256.

(4) Output after Reset

At reset, the output of ports P00–P02 and P04–P07 is in the high-

impedance state, port P50 outputs “L,” and the contents of the PWM

PWM output is undefined until setting the PWM register.

M37271MF-252SP Datasheet(PDF) 22 Page - Mitsubishi Electric Semiconductor

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