Timer Modules - Tm; Introduction; Tm Operation; Tm Clock Source - Holtek HT67F2350 Manual

HT67F2350/HT67F2360
HT67F2370/HT67F2390
Advanced A/D Flash MCU with LCD & EEPROM
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 device includes 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 Standard and Periodic TM sections.

Introduction

These devices contain several TMs and each individual TM can be categorised as a certain type,
namely Standard 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 Standard and Periodic 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.
TM Function
Timer/Counter
Input Capture
Compare Match Output
PWM Channels
Single Pulse Output
PWM Alignment
PWM Adjustment Period & Duty

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 xTnCK2~xTnCK0 bits in the
xTMn control registers, where "x" stands for S or P type TM and "n" stands for the specific TM
serial number. The clock source can be a ratio of the system clock, f
f , the f clock source or the external xTCKn pin. The xTCKn pin clock source is used to allow an
H SUB
external signal to drive the TM as an external clock source for event counting.
Rev. 1.60
STM
√
√
√
1
1
Edge
Duty or Period
TM Function Summary
133
PTM
√
√
√
1
1
Edge
Duty or Period
, or the internal high clock,
SYS
May 16, 2019