Timer Modules - Tm; Tm Ope�Ation - Holtek BS83B24C Manual

Timer Modules – TM
One of the most fundamental functions in any microcontroller devices is the ability to control and
measure time. To implement time related functions the devices include several Timer Modules,
generally abbreviated to the name TM. The TMs are multi-purpose timing units and serve to provide
operations such as Timer/Counter, Input Capture, Compare Match Output and Single Pulse Output
as well as being the functional unit for the generation of PWM signals. Each of the TMs has two
interrupts. The addition of input and output pins for each TM ensures that users are provided with
timing units with a wide and flexible range of features.
The common features of the different TM types are described here with more detailed information
provided in the individual Compact and Periodic Type TM sections.
Introduction
These devices contain several TMs and each individual TM can be categorised as a certain type,
namely Compact Type TM or Periodic Type TM. Although similar in nature, the different TM types
vary in their feature complexity. The common features to all of the Compact and Periodic type TMs
will be described in this section and the detailed operation regarding each of the TM types will be
described in separate sections. The main features and differences between the two types of TMs are
summarised in the accompanying table.
Time�/Co�nte�
Inp�t Capt��e
Compa�e Match O�tp�t
PWM Channels
Single P�lse O�tp�t
PWM Alignment
PWM Adj�stment Pe�iod & D�t�
Device
BS�3B�4C
BS�3C40C
TM Operation
The 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 count-up counter whose value is then compared with the value of pre-programmed internal
comparators. When the free running count-up 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.
TM Clock Source
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 xTCK2~xTCK0 bits in the
xTM control registers, where "x" stands for C or P type TM. The clock source can be a ratio of
the system clock, f
pin. The xTCK pin clock source is used to allow an external signal to drive the TM as an external
clock source for event counting.
Rev. 1.00
TM Function
D�t� o� Pe�iod
TM Function Summary
CTM
—
10-�it CTM
TM Name/Type Summary
, or the internal high clock, f
SYS
�6
BS83B24C/BS83C40C
Touch Flash MCU
CTM PTM
√ √
— √
√ √
1 1
— 1
Edge Edge
D�t� o� Pe�iod
PTM
10-�it PTM
10-�it PTM
, the f clock source or the external xTCK
H SUB
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