BS85B12-3 HOLTEK [Holtek Semiconductor Inc], BS85B12-3 Datasheet - Page 63

• Manufacturer Part Number: BS85B12-3
• Description: Touch Key Flash Type 8-Bit MCU with LCD/LED Driver
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

BS85B12-3/BS85C20-3
Touch Key Flash MCU with LCD/LED Driver
Timer Modules - TM
Rev. 1.00
Introduction
TM Operation
One of the most fundamental functions in any microcontroller device is the ability to control and
measure time. To implement time related functions each device includes several Timer Modules,
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 either two or three
individual 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, Standard and Enhanced TM sections.
The devices contain from two to three TMs depending upon which device is selected with each TM
having a reference name of TM0, TM1 and TM2. Each individual TM can be categorised as a certain
type, namely Compact Type TM, Standard Type TM or Enhanced Type TM. Although similar in
nature, the different TM types vary in their feature complexity. The common features to all of the
Compact, Standard and Enhanced TMs will be described in this section, the detailed operation
regarding each of the TM types will be described in separate sections. The main features and
differences between the three types of TMs are summarised in the accompanying table.
Each device in the series contains a specific number of either Compact Type, Standard Type and En-
hanced Type TM units which are shown in the table together with their individual reference name,
TM0~TM2.
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.
Timer/Counter
I/P Capture
Compare Match Output
PWM Channels
Single Pulse Output
PWM Alignment
PWM Adjustment Period & Duty
BS85C20-3
BS85B12-3
Device
Function
10-bit CTM
10-bit CTM
TM Name/Type Reference
TM0
TM Function Summary
Duty or Period
57
Edge
CTM
1
10-bit ETM
10-bit ETM
TM1
Duty or Period
Edge
STM
1
1
10-bit STM
TM2
Edge & Centre
Duty or Period
ETM
2
2
February 1, 2011