M37212 Mitsubishi, M37212 Datasheet - Page 44

• Manufacturer Part Number: M37212
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
• Manufacturer: Mitsubishi

8.7 PWM OUTPUT FUNCTION
This microcomputer is equipped with two 14-bit PWM (DA) and eight
8-bit PWMs (PWM0–PWM7). DA1 and DA2 have a 14-bit resolution
with the minimum resolution bit width of 0.25 s and a repeat period
of 4096 s (for f(X
structure and an 8-bit resolution with minimum resolution bit width of
4 s and repeat period of 1024 s (for f(X
Figure 8.7.1 shows the PWM block diagram. The PWM timing gen-
erating circuit applies individual control signals to DA and PWM0–
PWM7 using f(X
8.7.1 Data Setting
When outputting DA, first set the high-order 8 bits to the DA-H regis-
ter (address 00CE
(address 00CF
data to the PWMi register (i means 0 to 7; addresses 00D0
00D4
8.7.2 Transferring Data from Registers to PWM
Data transfer from the 8-bit PWM register to the 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.
Also, data transfer from the DA register (addresses 00CE
00CF
DA-L register (address 00CF
(address 00CE
it is possible to confirm the data being output from the DA output pin
by reading the DA register.
8.7.3 Operating of 8-bit PWM
The following explains PWM operation.
First, set the bit 0 of PWM output control register 1 (address 00D5
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 P6
also used as ports P0
the corresponding bits of the ports P6 direction register to “1” (output
mode). For PWM4–PWM7, set those of the port P0 direction regis-
ter to “1.” And select each output polarity by bit 3 of PWM output
control register 2 (address 00D6
bits 2 to 7 of PWM output control register 1 to “1” (PWM output). For
PWM6 and PWM7, set bits 0 and 1 of PWM output control register 2
to “1.”
The PWM waveform is output from the PWM output pins by setting
these registers.
Figure 8.7.2 shows the 8-bit PWM timing. One cycle (T) is com-
posed of 256 (2
weight of each bit (bits 0 to 7), are output inside the circuit during 1
cycle. Refer to Figure 8.7.2 (a). The 8-bit PWM outputs waveform
which is the logical sum (OR) of pulses corresponding to the con-
tents of bits 0 to 7 of the 8-bit PWM register. Several examples are
shown in Figure 8.7.2 (b). 256 kinds of output (HIGH area: 0/256 to
255/256) are selected by changing the contents of the PWM regis-
ter. A length of entirely HIGH output cannot be output, i.e. 256/256.
44
16
16
, 00F6
) to the 14-bit PWM circuit is executed at writing data to the
Circuit
16
16
16
8
IN
to 00F8
). When outputting PWM0–PWM7, set 8-bit output
) means reading this transferred data. Accordingly,
) segments. The 8 kinds of pulses, relative to the
IN
) divided by 2 as a reference signal.
16
) = 8 MHz). PWM0–PWM7 have the same circuit
), then the low-order 6 bits to the DA-L register
0
–P0
16
).
3
, respectively. For PWM0–PWM3, set
16
). Reading from the DA-H register
16
). Then, for PWM0–PWM5, set
0
–P6
IN
) = 8 MHz).
M37212M4/M8–XXXSP, M37212M6–XXXSP/FP
3
, PWM4–PWM7 are
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
16
16
and
16
to
)
8.7.4 Operating of 14-bit PWM
As with 8-bit PWM, set the bit 0 of PWM output control register 1
(address 00D5
cally), so that the PWM count source is supplied. Next, select the
output polarity by bit 2 of PWM output control register 2 (address
00D6
setting bit 1 of PWM output control register 1 to “0” (at reset, this bit
already set to “0” automatically) to select the DA output.
The output example of the 14-bit PWM is shown in Figure 8.7.3.
The 14-bit PWM divides the data of the DA latch into the low-order 6
bits and the high-order 8 bits.
The fundamental waveform is determined with the high-order 8-bit
data “D
mental waveform) is output every short area of “t” = 256 =
64 s ( is the minimum resolution bit width of 250 ns). The HIGH
level area increase interval (t
data “D
longer by t than that of other smaller intervals in PWM repeat period
“T” = 64t. Thus, a rectangular waveform with the different HIGH width
is output from the DA pins. Accordingly, the PWM output changes by
registers. A length of entirely HIGH cannot be output, i. e. 256/256.
8.7.5 Output after Reset
At reset, the output of ports P6
impedance state, and the contents of the PWM register and the
PWM circuit are undefined. Note that after reset, the PWM output is
undefined until setting the PWM register.
Table 8.7.1 Relation Between the Low-order 6-bit Data and High-
Low-order 6 bits of Data
unit pulse width by changing the contents of the DA-H and DA-L
0 0 0 0 0 0
0 0 0 0 0 1
0 0 0 0 1 0
0 0 0 1 0 0
0 0 1 0 0 0
0 1 0 0 0 0
1 0 0 0 0 0
16
L
). Then, the 14-bit PWM outputs from the DA output pin by
H
.” The HIGH are of smaller intervals “t
.” A HIGH area with a length t
LSB
level Area Increase Interval
16
Area Longer by than That of Other t
Nothing
m = 32
m = 16, 48
m = 8, 24, 40, 56
m = 4, 12, 20, 28, 36, 44, 52, 60
m = 2, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62
m = 1, 3, 5, 7, ................................. 57, 59, 61, 63
) to “0” (at reset, bit 0 is already set to “0” automati-
with ON-SCREEN DISPLAY CONTROLLER
MITSUBISHI MICROCOMPUTERS
m
) is determined with the low-order 6-bit
0
M37212EFSP/FP
–P6
3
and P0
D
H
0
m
(HIGH area of funda-
–P0
” shown in Table 5 is
3
m
are in the high-
(m = 0 to 63)
Rev. 1.0