Rev. 1.10
72
November 26, 2019
Rev. 1.10
73
November 26, 2019
HT68FB240
USB Low Speed Flash MCU
Timer/Counter Mode
To select this mode, bits TnM1 and TnM0 in the TMnC1
register should be set to "11" respectively.
The
Timer/Counter Mode operates in an identical way to the
Compare Match Output Mode
generating the same interrupt
flags. The exception is that in the Timer/Counter
Mode the TM output
pin is not used. Therefore the
above description and Timing Diagrams for the Compare
Match
Output Mode can be used to understand its
function. As the TM output pin is not used in this mode,
the pin can be used as a normal I/O pin or other
pin-shared function.
PWM Output Mode
To select this mode, bits TnM1 and TnM0 in the TMnC1
register should be set to "10" respectively.
The
PWM
function
within the TM is useful for applications which require
functions such as motor
control, heating control, illumination
control etc. By providing a signal of fixed frequency
but
of varying duty cycle on the TM output pin, a
square wave AC waveform can be generated with
varying
equivalent DC RMS values.
As both the period and duty cycle of the PWM waveform
can be controlled, the choice of generated
waveform is
extremely flexible. In the PWM mode, the TnCCLR bit
has no effect on the PWM
operation. Both of the CCRA
and CCRP registers are used to generate the PWM
waveform, one
register is used to clear the internal
counter and thus control the PWM waveform frequency,
while
the other one is used to control the duty cycle.
Which register is used to control either frequency
or duty
cycle is determined using the TnDPX bit in the TMnC1
register. The PWM waveform
frequency and duty cycle
can therefore be controlled by the values in the CCRA
and CCRP registers.
An interrupt flag, one for each of the CCRA and CCRP,
will be generated when a compare match
occurs from
either Comparator A or Comparator P. The TnOC bit in
the TMnC1 register is used to
select the required polarity
of the PWM waveform while the two TnIO1 and
TnIO0 bits are used to
enable the PWM output or to
force the TM output pin to a fixed high or low level. The
TnPOL bit is
used to reverse the polarity of the PWM
output waveform.
10-bit CTM, PWM Mode, Edge-aligned Mode, TnDPX=0
CCRP
001b
010b
011b
100b
101b
110b
111b
000b
Period
128
256
384
512
640
768
896
1024
Duty
CCRA
If f
SYS
= 16MHz, TM clock source select f
SYS
/4, CCRP =
100b
and CCRA = 128,
The
C
TM PWM output frequency = (f
SYS
/4)/512 = f
SYS
/2048 = 7.8125kHz, duty = 128/
512
= 25%.
If the Duty value defined by the CCRA register is equal to or greater than the Period value, then the
PWM output duty is 100%.
10-bit CTM, PWM Mode, Edge-aligned Mode, TnDPX=1
CCRP
001b
010b
011b
100b
101b
110b
111b
000b
Period
CCRA
Duty
128
256
384
512
640
768
896
1024
The PWM output period is determined by the CCRA register value together with the TM clock
while the PWM duty cycle is defined by the CCRP register value.