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Rev. 1.21
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HT66F488/HT66F489
A/D Flash MCU with EEPROM
HT66F488/HT66F489
A/D Flash MCU with EEPROM
Timer/Counter Mode
To select this mode, bits CTM1 and CTM0 in the CTMC1 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 CTM1 and CTM0 in the CTMC1 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 CTCCLR bit has no effect as the PWM
period. 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 CTDPX bit in the CTMC1 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 CTOC bit In the CTMC1 register is used to
select the required polarity of the PWM waveform while the two CTIO1 and CTIO0 bits are used to
enable the PWM output or to force the TM output pin to a fixed high or low level. The CTPOL bit is
used to reverse the polarity of the PWM output waveform.
•
CTM, PWM Mode, Edge-aligned Mode, CTDPX=0
CCRP
001b
010b
011b
100b
101b
110b
111b
000b
Pe�iod
128
256
384
512
64�
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8�6
1�24
Duty
CCRA
If f
SYS
= 16MHz, TM clock source is f
SYS
/4, CCRP = 100b, CCRA =128,
The CTM PWM output frequency = (f
SYS
/4) /512 = f
SYS
/2048 = 7.8125 kHz, 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%.
•
CTM, PWM Mode, Edge-aligned Mode, CTDPX=1
CCRP
001b
010b
011b
100b
101b
110b
111b
000b
Pe�iod
CCRA
Duty
128
256
384
512
64�
�68
8�6
1�24
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.