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Under
development
Mitsubishi microcomputers
M30201 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Timer A
(4) Pulse width modulation (PWM) mode
In this mode, the timer outputs pulses of a given width in succession. (See Table 1.17.) In this mode, the counter
functions as either a 16-bit pulse width modulator or an 8-bit pulse width modulator. Figure 1.45 shows the timer
A0 mode register in pulse width modulation mode. Figure 1.46 shows the example of how a 16-bit pulse width
modulator operates. Figure 1.47 shows the example of how an 8-bit pulse width modulator operates.
Figure 1.45. Timer A0 mode register in pulse width modulation mode
Table 1.17. Timer specifications in pulse width modulation mode
Item
Specification
Count source
f1, f8, f32, fc32
Count operation
The timer counts down (operating as an 8-bit or a 16-bit pulse width modulator)
The timer reloads a new count at a rising edge of PWM pulse and continues counting
The timer is not affected by a trigger that occurs when counting
16-bit PWM
High level width
n / fi
n : Set value
Cycle time
(216-1) / fi fixed
8-bit PWM
High level width n
(m+1) / fi n : values set to timer A0 register’s high-order address
Cycle time (28-1)
(m+1) / fi m : values set to timer A0 register’s low-order address
Count start condition
External trigger is input
The timer overflows
The count start flag is set (= 1)
Count stop condition
The count start flag is reset (= 0)
8 bits PWM
Set value of "H" level width is except FF16, 0016 : PWM pulse goes “L”
Set value of "H" level width is FF16, 0016 : Timing that count value goes to 0116
16 bits PWM
Set value of "H" level width is except FFFF16, 000016 : PWM pulse goes “L”
Set value of "H" level width is FFFF16, 000016 : Timing that count value goes to 000116
TA0IN pin function
Programmable I/O port or trigger input
TA0OUT pin function
Pulse output
Read from timer
When timer A0 register is read, it indicates an indeterminate value
Write to timer
When counting stopped :When a value is written to timer A0 register, it is
written to both reload register and counter
When counting in progress : When a value is written to timer A0 register, it is
written to only reload register (Transferred to counter at next reload time)
Bit name
Function
Bit symbol
Operation mode
select bit
1 1 : PWM mode
b1 b0
TMOD1
TMOD0
MR0
MR2
MR1
MR3
0 0 : f1
0 1 : f8
1 0 : f32
1 1 : fC32
b7 b6
TCK1
TCK0
Count source select bit
W
R
11
1
1 (Must always be “1” in PWM mode)
16/8-bit PWM mode
select bit
0: Functions as a 16-bit pulse width modulator
1: Functions as an 8-bit pulse width modulator
Trigger select bit
External trigger select
bit (Note 1)
0: Falling edge of TA0IN pin's input signal (Note 2)
1: Rising edge of TA0IN pin's input signal (Note 2)
0: Count start flag is valid
1: Selected by event/trigger select register
Note 1: Valid only when the TA0IN pin is selected by the event/trigger select bit
(addresses 038316). If timer overflow is selected, this bit can be “1” or “0”.
Note 2: Set the corresponding port direction register to “0” (input mode).
Note 3: Set the corresponding port direction register to “1” (output mode) when the pulse is output.
Timer A0 mode register
Symbol
Address
When reset
TA0MR
039616
0016
b7 b6
b5
b4
b3
b2
b1 b0
Interrupt
request
generation
timing
Note: When set value of "H" level width is 0016 or 000016, pulse outputs "L" level and inversion value, FF16 or FFFF16 is set to timer.