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80
TimerA
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
(4) Pulse width modulation (PWM) mode
In this mode, the timer outputs pulses of a given width in succession. (See Table 20.) In this mode, the counter
functions as either a 16-bit pulse width modulator or an 8-bit pulse width modulator. Figure 63 shows the timer
Ai mode register in pulse width modulation mode. Figure 64 shows the example of how a 16-bit pulse width
modulator operates. Figure 65 shows the example of how an 8-bit pulse width modulator operates.
Table 20. Timer specifications in pulse width modulation mode
Figure 63. Timer Ai mode register 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 X (m+1) / fi
n : values set to timer Ai register’s high-order address
Cycle time
(28-1) X (m+1) / fi
m : values set to timer Ai 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)
Interrupt request generation timing
PWM pulse goes “L”
TAiIN pin function
Programmable I/O port or trigger input
TAiOUT pin function
Pulse output
Read from timer
When timer Ai register is read, it indicates an indeterminate value
Write to timer
When counting stopped
When a value is written to timer Ai register, it is written to both reload
register and counter
When counting in progress
When a value is written to timer Ai register, it is written to only reload register
(Transferred to counter at next reload time)
Timer Ai mode register
SymbolAddressWhen reset
TAiMR(i=0 to 4)039616 to 039A16
0016
Bit nameFunction
Bit symbol
b7
b6b5b4b3
b2b1b0
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 fixed to “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 TAiIN pin's input signal (Note 2)
1: Rising edge of TAiIN 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 TAiIN pin is selected by the event/trigger select bit
(addresses 038216 and 038316). If timer overflow is selected, this bit can be “1” or “0
Note 2: Set the corresponding port direction register to “0”.