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T IME R A
7721 Group User’s Manual
8–39
8.6 Pulse width modulation (PWM) mode
Fig. 8.6.1 Structures of timer Aj mode registers and timer Aj registers in PWM mode
b7
b6
b5
b4
b3
b2
1
b1
1
b0
1
Timer Aj mode register (j = 2 to 4) (Addresses 58
16
to 5A
16
)
7
2
0 1 : f
16
1 0 : f
64
1 1 : f
512
b7 b6
Count source select bits
At reset
0
RW
Trigger select bits
Fix this bit to “1” in PWM mode.
1
Operating mode select bits
Functions
1 1 : PWM mode
b1 b0
b4 b3
0 0 :
Writing “1” to count start register
0 1 :
grammable I/O port.)
1 0 :
Falling edge of TAj
IN
pin’s input signal
1 1 :
Rising edge of TAj
IN
pin’s input signal
16/8-bit PWM mode select bit
IN
pin functions as a pro-
0 : 16-bit pulse width modulator
1 : 8-bit pulse width modulator
4
0
2
3
5
6
0
0
0
0
0
0
0
RW
RW
RW
RW
RW
RW
RW
RW
<When operating as an 8-bit pulse width modulator>
(b15)
b7
b0
b7
b0
(b8)
Timer A2 register (Addresses 4B
16
, 4A
16
)
Timer A3 register (Addresses 4D
16
, 4C
16
)
Timer A4 register (Addresses 4F
16
, 4E
16
)
Functions
Bit
At reset
RW
7 to 0
15 to 8
Undefined
Undefined
These bits can be set to “00
16
” to “FF
16
.”
Assuming that the set value = m, PWM
pulse’s period output from the TAj
OUT
pin is
expressed as follows:
(m + 1)(2
8
– 1)
f
i
WO
These bits can be set to “00
16
” to “FE
16
.”
Assuming that the set value = n, the “H” level
width of the PWM pulse output from the
TAj
OUT
pin is expressed as follows:
n(m + 1)
f
i
f
i
: Frequency of count source (f
2
, f
16
, f
64
, or f
512
)
Note:
Use the
LDM
or
STA
instruction for writing to this register.
Read from or write to this register in a unit of 16 bits.
WO
b7
b0
b7
b0
Timer A2 register (Addresses 4B
16
, 4A
16
)
Timer A3 register (Addresses 4D
16
, 4C
16
)
Timer A4 register (Addresses 4F
16
, 4E
16
)
Functions
Bit
At reset
RW
15 to 0 These bits can be set to “0000
16
” to “FFFE
16
.”
Assuming that the set value = n, the “H” level
width of the PWM pulse output from the
TAj
OUT
pin is expressed as follows:
(PWM pulse period =
)
Undefined
<When operating as a 16-bit pulse width modulator>
(b15)
(b8)
WO
n
f
i
f
i
: Frequency of count source (f
2
, f
16
, f
64
, or f
512
)
Note:
Use the
LDM
or
STA
instruction for writing to this register.
Read from or write to this register in a unit of 16 bits.
n
16
– 1
f
i
Bit
Bit name
(TAj