HT46R232/HT46C232
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from an external source or an internal clock source. An
internal clock source comes from fSYS/4. The external
clock input allows the user to count external events,
measure time intervals or pulse widths, or to generate
an accurate time base.
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There are six registers related to the Timer/Event Coun-
ter 0; TMR0H (0CH), TMR0L (0DH), TMR0C (0EH) and
the Timer/Event Counter 1; TMR1H (0FH), TMR1L
(10H), TMR1C (11H). Writing TMR0L (TMR1L) will only
put the written data to an internal lower-order byte buffer
(8-bit) and writing TMR0H (TMR1H) will transfer the
specified data and the contents of the lower-order byte
buffer to TMR0H (TMR1H) and TMR0L (TMR1L) regis-
ters, respectively. The Timer/Event Counter 1/0 preload
register is changed by each writing TMR0H (TMR1H)
operations. Reading TMR0H (TMR1H) will latch the
contents of TMR0H (TMR1H) and TMR0L (TMR1L)
counters to the destination and the lower-order byte
buffer, respectively. Reading the TMR0L (TMR1L) will
read the contents of the lower-order byte buffer. The
TMR0C (TMR1C) is the Timer/Event Counter 0 (1) con-
trol register, which defines the operating mode, counting
enable or disable and an active edge.
Reset Timing Chart
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Reset Configuration
TO PDF
RESET Conditions
RES reset during power-up
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RES reset during normal operation
RES wake-up HALT
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.
WDT time-out during normal operation
WDT wake-up HALT
Note: ²u² stands for ²unchanged²
To guarantee that the system oscillator is started and
stabilized, the SST (System Start-up Timer) provides an
extra-delay of 1024 system clock pulses when the sys-
tem awakes from the HALT state or during power up.
Awaking from the HALT state or system power up an
SST delay is added. An extra SST delay is added during
power up period, and any wake-up from HALT may en-
able only the SST delay. The functional unit chip reset
status are shown below.
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. Once an over-
flow occurs, the counter is reloaded from the timer/event
counter preload register, and generates an interrupt re-
quest flag (T0F; bit 5 of INTC0, T1F; bit 6 of INTC0).
Program Counter
Interrupt
000H
Disable
Cleared
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 ²0²), 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,
the timer/event counter begins counting not according
to the logic level but to the transient edges. In the case of
counter overflows, the counter is reloaded from the
timer/event counter register and issues an interrupt re-
quest, as in the other two modes, i.e., event and timer
modes.
Prescaler, Divider
Clear. After master reset,
WDT begins counting
WDT
Timer/event Counter Off
Input/output Ports
Stack Pointer
Input mode
Points to the top of the stack
Timer/Event Counter
Two Timer/Event Counters (TMR0,TMR1) are imple-
mented in the microcontroller. The timer/event counter 0
contains an 16-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
SYS. The timer/event counter 1 contains an 16-bit pro-
grammable count-up counter and the clock may come
Rev. 1.50
13
January 21, 2009
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
