HT46R64/HT46C64
Timer/Event Counter
internal lower-order byte buffer (8-bit) and writing
TMR1H will transfer the specified data and the contents
of the lower-order byte buffer to TMR1H and TMR1L
registers, respectively.
Two timer/event counters (TMR0,TMR1) are imple-
mented in the microcontroller. The Timer/Event Counter
0 contains a 8-bit programmable count-up counter and
the clock may come from an external source or an inter-
nal clock source. An internal clock source comes from
fSYS. The Timer/Event Counter 1 contains a 16-bit pro-
grammable count-up counter and the clock may come
from an external source or an internal clock source. An
internal clock source comes from fSYS/4 or 32768Hz se-
lected by option. The external clock input allows the
user to count external events, measure time intervals or
pulse widths, or to generate an accurate time base.
The Timer/Event Counter 1 preload register is changed
everytime there is a writing operation to TRM1H. Read-
ing TMR1H will latch the contents of TMR1H and
TMR1L counters to the destination and the lower-order
byte buffer, respectively. Reading the TMR1L will read
the contents of the lower-order byte buffer. The TMR1C
is the Timer/Event Counter 1 control register, which de-
fines the operating mode, counting enable or disable
and an active edge.
There are two registers related to the Timer/Event
Counter 0; TMR0 ([0DH]) and TMR0C ([0EH]). Two
physical registers are mapped to TMR0 location; writing
TMR0 puts the starting value in the Timer/Event Coun-
ter 0 register and reading TMR0 takes the contents of
the Timer/Event Counter 0. The TMR0C is a timer/event
counter control register, which defines some options.
There are three registers related to the Timer/Event
Counter 1; TMR1H (0FH), TMR1L (10H) and TMR1C
(11H). Writing TMR1L will only put the written data to an
The T0M0, T0M1 (TMR0C) and T1M0, T1M1 (TMR1C)
bits define the operation mode. The event count mode is
used to count external events, which means that the
clock source is from an external (TMR0, TMR1) pin. The
timer mode functions as a normal timer with the clock
source coming from the internal selected clock source.
Finally, the pulse width measurement mode can be used
to count the high or low level duration of the external sig-
nal (TMR0, TMR1), and the counting is based on the in-
ternal selected clock source.
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PFD Source Option
Rev. 1.80
17
February 14, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
