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參數(shù)資料
| 型號： | HT49R50A |
| 廠商： | Holtek Semiconductor Inc. |
| 英文描述： | 8-Bit High Performance High speed Microcontroller(8位、高性能、高速微控制器) |
| 中文描述： | 8位高性能高速微控制器（8位，高性能，高速微控制器） |
| 文件頁數(shù)： | 16/51頁 |
| 文件大?。?/td> | 320K |
| 代理商： | HT49R50A |
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HT49R50A
16
November 29, 2000
ETBI, and ERTI are all used to control the en-
able/disable status of interrupts. These bits
prevent the requested interrupt from being ser-
viced. Once the interrupt request flags (RTF,
TBF, T0F, T1F, EIF1, EIF0) are all set, they re-
main in the INTC1 or INTC0 respectively until
the interrupts are serviced or cleared by a soft-
ware instruction.
It is recommended that a program not use the
"CALL subroutine" within the interrupt subrou-
tine. Its because interrupts often occur in an un-
predictable manner or require to be serviced
immediately in some applications. At this time, if
onlyonestackisleft,andenablingtheinterruptis
not well controlled, operation of the "call" in the
interrupt subroutine may damage the original
control sequence.
Oscillator configuration
The HT49R50A provides three oscillator cir-
cuits for system clocks, .e., RC oscillator, crystal
oscillator and 32768Hz crystal oscillator, deter-
mined by options. No matter what type of oscil-
lator is selected, the signal is used for the
system clock. The HALT mode stops the system
oscillator (RC and crystal oscillator only) and
ignores external signal to conserve power. The
32768Hz crystal oscillator (system oscillator)
still runs at HALT mode. If the 32768Hz crystal
oscillator is selected as the system oscillator,
the system oscillator is not stopped; but the in-
struction execution is stopped. Since the (used
as system oscillator or RTC oscillator) is also
designed for timing purposes, the internal tim-
ing (RTC, time base, WDT) operation still runs
even if the system enters the HALT mode.
Of the three oscillators, if the RC oscillator is
used, an external resistor between OSC1 and
VSS is required, and the range of the resistance
should be from 40k
clock, divided by 4, is available on OSC2 with
pull-high resistor, which can be used to syn-
chronize external logic. The RC oscillator pro-
vides the most cost effective solution. However,
the frequency of the oscillation may vary with
VDD, temperature, and the chip itself due to
process variations. It is therefore, not suitable
for timing sensitive operations where accurate
oscillator frequency is desired.
to 680k . The system
On the other hand, if the crystal oscillator is se-
lected, a crystal across OSC1 and OSC2 is
needed to provide the feedback and phase shift
required for the oscillator, and no other exter-
nal components are required. A resonator may
be connected between OSC1 and OSC2 to re-
place the crystal and to get a frequency refer-
ence, but two external capacitors in OSC1 and
OSC2 are required.
There is another oscillator circuit designed for
the real time clock. In this case, only the
32.768kHz crystal oscillator can be applied.
The crystal should be connected between OSC3
and OSC4.
The RTC oscillator circuit can be controlled to
oscillate quickly by setting the "QOSC" bit (bit
4 of RTCC). It is recommended to turn on the
quick oscillating function upon power on, and
then turn it off after 2 seconds.
The WDT oscillator is a free running on-chip
RC oscillator, and no external components are
required. Although the system enters the
power down mode, the system clock stops, and
the WDT oscillator still works with a period of
approximately 78 s. The WDT oscillator can be
disabled by options to conserve power.
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System oscillator
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