HT68F14 HOLTEK [Holtek Semiconductor Inc], HT68F14 Datasheet - Page 58

• Manufacturer Part Number: HT68F14
• Description: Enhanced I/O Flash Type MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

HT68F13/HT68F14/HT68F15
Enhanced I/O Flash Type MCU
Rev. 1.10
TM Operation
TM Clock Source
TM Interrupts
TM External Pins
The three different types of TM offer a diverse range of functions, from simple timing operations to
PWM signal generation. The key to understanding how the TM operates is to see it in terms of a free
running counter whose value is then compared with the value of pre-programmed internal
comparators. When the free running counter has the same value as the pre-programmed comparator,
known as a compare match situation, a TM interrupt signal will be generated which can clear the
counter and perhaps also change the condition of the TM output pin. The internal TM counter is driven
by a user selectable clock source, which can be an internal clock or an external pin.
The clock source which drives the main counter in each TM can originate from various sources. The
selection of the required clock source is implemented using the TnCK2~TnCK0 bits in the TM control
registers. The clock source can be a ratio of either the system clock f
f
reserved clock input, in effect disconnecting the TM clock source. The TCKn pin clock source is used
to allow an external signal to drive the TM as an external clock source or for event counting.
The Compact and Standard type TMs each have two internal interrupts, one for each of the internal
comparator A or comparator P, which generate a TM interrupt when a compare match condition
occurs. As the Enhanced type TM has three internal comparators and comparator A or comparator B or
comparator P compare match functions, it consequently has three internal interrupts. When a TM
interrupt is generated it can be used to clear the counter and also to change the state of the TM output
pin.
Each of the TMs, irrespective of what type, has one TM input pin, with the label TCKn. The TM input
pin, is essentially a clock source for the TM and is selected using the TnCK2~TnCK0 bits in the
TMnC0 register. This external TM input pin allows an external clock source to drive the internal TM.
This external TM input pin is shared with other functions but will be connected to the internal TM if
selected using the TnCK2~TnCK0 bits. The TM input pin can be chosen to have either a rising or
falling active edge.
The TMs each have one or more output pins with the label TPn. When the TM is in the Compare
Match Output Mode, these pins can be controlled by the TM to switch to a high or low level or to
toggle when a compare match situation occurs. The external TPn output pin is also the pin where the
TM generates the PWM output waveform. As the TM output pins are pin-shared with other function,
the TM output function must first be setup using registers. A single bit in one of the registers
determines if its associated pin is to be used as an external TM output pin or if it is to have another
function. The number of output pins for each TM type and device is different, the details are provided
in the accompanying table.
TBC
clock source or the external TCKn pin. Note that setting these bits to the value 101 will select a
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or the high speed clock f
February 9, 2011
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