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| 型號(hào)： | HT49R30 |
| 廠商： | Holtek Semiconductor Inc. |
| 英文描述： | DISPLAY 7 SEGMENT |
| 中文描述： | 8位LCD型微控制器 |
| 文件頁數(shù)： | 17/43頁 |
| 文件大小： | 353K |
| 代理商： | HT49R30 |
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HT49R30A-1/HT49C30-1/HT49C30L
Rev. 1.10
17
September 25, 2002
Timer/Event Counter
One timer/event counters is implemented in the device.
It contains an 8-bit programmable count-up counter.
The timer/event counter clock source may come from
the system clock or system clock/4 or RTC time-out sig-
nal or external source. System clock source or system
clock/4 is selected by options. Using external clock input
allows the user to count external events, measure time
internals or pulse widths, or generate an accurate time
base. While using the internal clock allows the user to
generate an accurate time base.
There are two registers related to the timer/event coun-
ter, i.e., TMR ([0DH]) and TMRC ([0EH]). There are also
two physical registers which are mapped to TMR loca-
tion; writing TMR places the starting value in the
timer/event counter preload register, while reading it
yields the contents of the timer/event counter. TMRC is
a timer/event counter control register used to define
some options.
The TN0 and TN1 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
TMR 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 signal TMR, and the counting is based on
the internal 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 FFH. Once an overflow
occurs, the counter is reloaded from the timer/event
counter preload register, and generates an interrupt re-
quest flag (TF; bit 6 of INTC0).
In the pulse width measurement mode with the values
of the TON and TE bits equal to one, after the TMR
has received a transient from low to high (or high to
low if the TE bit is 0 ), it will start counting until the
TMR returns to the original level and resets the TON.
The measured result remains in the timer/event counter
even if the activated transient occurs again. In other
words, only one cycle measurement can be made until
the TON is set. The cycle measurement will re-function
aslongasitreceivesfurthertransientpulse.Inthisoper-
ation mode, the timer/event counter begins counting ac-
cording not to the logic level but to the transient edges.
In the case of counter overflows, the counter is reloaded
from the timer/event counter preload register and issues
an interrupt request, as in the other two modes, i.e.,
event and timer modes.
To enable the counting operation, the Timer ON bit
(TON; bit 4 of TMRC) should be set to 1. In the pulse
width measurement mode, the TON is automatically
cleared after the measurement cycle is completed. But
in the other two modes, the TON can only be reset by in-
structions. The overflow of the Timer/Event Counter is
one of the wake-up sources and can also be applied to a
PFD (Programmable Frequency Divider) output at PA3
by options. No matter what the operation mode is, writing
a 0 to ETI disables the related interrupt service. When the
PFD function is selected, executing CLR [PA].3 instruc-
tion to enable PFD output and executing SET [PA].3 in-
struction to disable PFD output.
In the case of timer/event counter OFF condition, writing
data to the timer/event counter preload register also re-
loads that data to the timer/event counter. But if the
timer/event counter is turn on, data written to the
timer/event counter is kept only in the timer/event coun-
ter preload register. The timer/event counter still contin-
ues its operation until an overflow occurs.
When the timer/event counter (reading TMR) is read,
the clock is blocked to avoid errors. As this may results
in a counting error, blocking of the clock should be taken
into account by the programmer.
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Timer/Event Counter
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| HT49R30A-1 | DISPL 7 SEG YELLOW |
| HT49C30-1 | 8-Bit LCD Type MCU |
| HT49C50 | 8-BIT MICROCONTROLLER |
| HT49R50A | 8-Bit High Performance High speed Microcontroller(8位、高性能、高速微控制器) |
| HT49R50 | 8-BIT MICROCONTROLLER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| HT49R30A-1 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:8-Bit LCD Type MCU |
| HT49R30A-1_12 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:LCD Type 8-Bit MCU |
| HT49R50 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:8-Bit Microcontroller |
| HT49R50(100QFP) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Microcontroller |
| HT49R50(80QFP) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Microcontroller |
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