HT37B90/HT37B70/HT37B50/HT37B30
Timer/Event Counters
The provision of timers form an important part of any
microcontroller, giving the designer a means of carrying
out time related functions. The devices contain two
count-up timers 8-bit capacity and one count-up timers
16-bit capacity. As the timer 0/1 has three different oper-
ating modes, they can be configured to operate as a
general timer, an external event counter or as a pulse
width measurement device. But the timer 2 only be con-
figured to operate as a general timer. The provision of an
internal prescaler to the clock circuitry of some of the
timer/event counters gives added range to the timer 1/2.
initial value can be preloaded. Reading from this register
retrieves the contents of the Timer/Event Counter. The
second type of associated register is the Timer Control
Register which defines the timer options and deter-
mines how the timer is to be used. The Timer/Event
Counter 0 can have the timer clock configured to come
from the internal clock source. The clock source is
fOSC/8.In addition, the timer clock source of Timer/Event
Counter 0 can also be configured to come from an inter-
nal RC 12kHz.
An external clock source is used when the timer is in the
event counting mode, the clock source being provided
on the external timer pin, known as TMR0 or TMR1.
These external timer pins are pin-shared with other I/O
pins. Depending upon the condition of PA share pin op-
tion, each high to low, or low to high transition on the ex-
ternal timer input pin will increment the counter by one.
There are three types of registers related to the
Timer/Event Counters 0. The first two register contain
the actual high and low byte value of the timer and into
which an initial value can be preloaded.
There are two types of registers related to the
Timer/Event Counters 1/2. The first is the register that
contains the actual value of the timer and into which an
16-bit Timer/Event Counter 0 Structure
8-bit Timer/Event Counter 1 Structure
8-bit Timer Counter 2 Structure
Rev. 1.00
23
June 22, 2017
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
