ht82a523r Holtek Semiconductor Inc., ht82a523r Datasheet - Page 15

• Manufacturer Part Number: ht82a523r
• Description: Ht82a523r -- Usb 2.0 Full Speed 8-bit Otp Mcu
• Manufacturer: Holtek Semiconductor Inc.

Timer/Event Counter
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
f
grammable count-up counter and the clock may come
from an external source or an internal clock source. An
internal clock source comes from f
clock input allows the user to count external events,
measure time intervals or pulse widths, or generate an
accurate time base.
There are five registers related to the Timer/Event
Counter 0; TMR0 (0DH), TMR0C (0EH) and the
Timer/Event Counter 1; TMR1H (0FH), TMR1L (10H),
TMR1C (11H). For 16bits timer to Write data to TMR1L
will only put the written data to an 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. The Timer/Event
Counter 1 preload register is changed by each writing
TMR1H operations. Reading TMR1H will latch the con-
tents 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 TMR0C (TMR1C) is the Timer/Event Coun-
ter 0 (1) control register, which defines the operating
mode, counting enable or disable and an active edge.
Rev. 1.30
SYS
. The Timer/Event Counter 1 contains a 16-bit pro-
SYS
/4. The external
Timer/Event Counter 0
Timer/Event Counter 1
15
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.
In the event count or timer mode, the timer/event coun-
ter starts counting at the current contents in the
timer/event counter and ends at FFFFH(for 16 bits timer
is FFFFH, bit 8 bits timer will be FFH). Once an overflow
occurs, the counter is reloaded from the timer/event
counter preload register, and generates an interrupt re-
quest flag (T0F; bit 5 of the INTC0, T1F; bit 6 of the
INTC0).
In the pulse width measurement mode with the values of
the T0ON/T1ON and T0E/T1E bits equal to 1, after the
TMR0 (TMR1) has received a transient from low to high
(or high to low if the T0E/T1E bit is 0 ), it will start count-
ing until the TMR0 (TMR1) returns to the original level
and resets the T0ON/T1ON. The measured result re-
mains in the timer/event counter even if the activated
transient occurs again. In other words, only 1-cycle
measurement can be made until the T0ON/T1ON is set.
The cycle measurement will re-function as long as it re-
ceives further transient pulse. In this operation mode,
HT82A523R
May 13, 2008