Pwm Timer Functions - Fujitsu F2MC-8L F202RA Hardware Manual

Note:
Calculation example of intervals and square wave frequency
The following expression is the interval when the count clock cycle is set to 1 t
oscillation frequency (F
are set. Another expression is the frequency of the square wave output from the PWM pin that is
operated continuously without changing the COMR register value.
However, the values are true when the maximum speed clock of the normal mode is selected (CS1,
CS0 = 11
■

PWM Timer Functions

The PWM timer functions have an 8-bit resolution and can control the "H" level width and "L" level width
of one cycle.
Because the resolution is 1/256, a pulse can be output at a duty ratio of 0 to 99.6%.
The frequency of the PWM wave can be selected from four types.
The low-pass filter can be connected to the output and used as the D/A converter.
Table 7.1-2 shows the frequency of the PWM wave that can be set by PWM timer functions. Figure 7.1-1 is
a configuration example of the D/A converter.
Table 7.1-2 Frequencies of the PWM Wave that can be Set by the PWM Timer Functions
Count clock cycle
PWM wave cycle
2
t : Instruction cycle (Affected by the clock mode and others.)
INST
t : Output frequency of an 8/16-bit capture timer
EXT
) of 12.5 MHz and a PWM compare register (COMR) value of DD
CH
, 1 instruction cycle = 4/F
B
= (1 × 4/F
Interval
= (4/12.5 MHz) × (221 + 1)
= 71.0 µs
Output frequency = F
= 12.5 MHz/ (8 × (221 + 1))
7.04 kHz
1 2
Internal clock
1t 16t 64t
INST INST
8 12 14
t 2 t 2
INST INST
) with the system clock control register (SYCC).
CH
) × (COMR register value + 1)
CH
/ (1 × 8 × (COMR register value + 1))
CH
3
Output of an 8/16-bit capture timer/counter
2
2 t to
INST
INST
10
2 t
INST
10
2 t to
INST
t
INST
18
2 t
INST
CHAPTER 7 8-BIT PWM TIMER
4
6 10
2 t to 2 t to
INST INST
14 18
2 t 2 t
INST INST
14 18
2 t to 2 t to
INST INST
22 26
2 t 2 t
INST INST
and when an
INST
(221)
H
1t to
EXT
8
2 t
EXT
8
2 t to
EXT
16
2 t
EXT
137