m37280eksp Mitsumi Electronics, Corp., m37280eksp Datasheet - Page 46

• Manufacturer Part Number: m37280eksp
• Description: Single-chip 8-bit Cmos Microcomputer With Closed Caption Decoder And On-screen Display Controller
• Manufacturer: Mitsumi Electronics, Corp.

46
12.7 PWM OUTPUT CIRCUIT
This microcomputer is equipped with eight 8-bit PWMs (PWM0–
PWM7). PWM0–PWM7 have the same circuit structure and an 8-bit
resolution with minimum resolution bit width of 4 s and repeat pe-
riod of 1024 s (for f(X
Figure 12.7.1 shows the PWM block diagram. The PWM timing gen-
erating circuit applies individual control signals to PWM0–PWM7 us-
ing f(X
12.7.1 Data Setting
register (i means 0 to 7; addresses 0200
12.7.2 Transmitting Data from Register to PWM
Data transfer from the PWM register to the PWM circuit is executed
at writing data to the register.
The signal output from the PWM output pin corresponds to the con-
tents of this register.
12.7.3 PWM Operation
The following explains PWM operation.
First, set the bit 0 of PWM mode register 1 (address 020A
(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 P0
also used as pins P0
P0
register to “1” (output mode). And select each output polarity by bit 3
of PWM mode register 1 (address 020A
PWM mode register 2 to “1” (PWM output).
The PWM waveform is output from the PWM output pins by setting
these registers.
Figure 12.7.2 shows the PWM timing. One cycle (T) is composed of
256 (2
each bit (bits 0 to 7), are output inside the circuit during 1 cycle.
Refer to Figure 12.7.2 (a). The PWM outputs waveform which is the
logical sum (OR) of pulses corresponding to the contents of bits 0 to
7 of the PWM register. Several examples are shown in Figure 12.7.2
(b). 256 kinds of output (HIGH area: 0/256 to 255/256) are selected
by changing the contents of the PWM register. A length of entirely
HIGH cannot be output, i.e. 256/256.
12.7.4 Output after Reset
At reset, the output of port P0 is in the high-impedance state, port
P5
circuit are undefined. Note that after reset, the PWM output is unde-
fined until setting the PWM register.
When outputting PWM0–PWM7, set 8-bit output data to the PWMi
3
0
outputs Low, and the contents of the PWM register and the PWM
respectively. Set the corresponding bits of the port P0 direction
8
IN
) segments. The 8 kinds of pulses, relative to the weight of
) divided by 2 as a reference signal.
circuit
0
–P0
IN
) = 8 MHz) .
2
, and PWM7 is also used as pin P5
16
16
4
–P0
). Then, set bits 7 to 0 of
to 0207
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
7
, PWM4–PWM6 are
16
).
M37280MF–XXXSP, M37280MK–XXXSP
16
) to “0”
0
and
and ON-SCREEN DISPLAY CONTROLLER
MITSUBISHI MICROCOMPUTERS
M37280EKSP
Rev. 1.0