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參數(shù)資料
| 型號： | P83CL782 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | Low voltage 8-bit microcontrollers with UART and I2C-bus |
| 中文描述： | 低電壓8 - UART及位微控制器的I2C總線 |
| 文件頁數(shù)： | 51/76頁 |
| 文件大?。?/td> | 342K |
| 代理商： | P83CL782 |
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1997 Mar 14
51
Philips Semiconductors
Product specification
Low voltage 8-bit microcontrollers with
UART and I
2
C-bus
P83CL781; P83CL782
17 RESET
To initialize the P83CL78x a reset is performed by either of
two methods:
Applying an external signal to the RST pin
Via Power-on reset circuitry.
The reset state of the port pins is mask-programmable and
can be defined by the user. The standard reset value for
Ports 0 to 3 is FFH. A reset leaves the internal registers as
shown in Chapter 18.
17.1
External reset using the RST pin
The reset input for the P83CL78x is RST. A Schmitt trigger
is used at the input for noise rejection. The output of the
Schmitt trigger is sampled by the reset circuitry every
machine cycle. A reset is accomplished by holding the
RST pin HIGH for at least two machine cycles
(24 oscillator periods) while the oscillator is running.
The CPU responds by executing an internal reset. Port
pins adopt their reset state immediately after the RST goes
HIGH. During reset, ALE and PSEN are held HIGH.
The external reset is asynchronous to the internal clock.
The RST pin is sampled during state 5, phase 2 of every
machine cycle. After a HIGH is detected at the RST pin, an
internal reset is repeated until RST goes LOW.
The internal RAM is not affected by reset. When V
DD
is
turned on, the RAM contents are indeterminate.
17.2
Power-on reset
The device contains on-chip circuitry which switches the
port pins to the customer defined logic level as soon as
V
DD
exceeds 1.3 V; if the mask option ‘ON’ has been
chosen. As soon as the minimum supply voltage is
reached, the oscillator will start up. However, to ensure
that the oscillator is stable before the controller starts, the
clock signals are gated away from the CPU for a further
1536 oscillator periods. A hysteresis of approximately
50 mV at a typical power-on switching level of 1.3 V will
ensure correct operation. See Fig.32.
The on-chip Power-on reset circuitry can also be switched
off via the mask option ‘OFF’. This option reduces the
Power-down current to typically 800 nA and can be
chosen if external reset circuitry is used. For applications
not requiring the internal reset, option ‘OFF’ should be
chosen.
An automatic reset can be obtained by connecting the RST
pin to V
DD
via a 10
μ
F capacitor. At power-on, the voltage
on the RST pin is equal to V
DD
minus the capacitor voltage,
and decreases from V
DD
as the capacitor charges through
the internal resistor (R
RST
) to ground. The larger the
capacitor, the more slowly V
RST
decreases. V
RST
must
remain above the lower threshold of the Schmitt trigger
long enough to effect a complete reset. The time required
is the oscillator start-up time, plus 2 machine cycles.
The Power-on reset circuitry is shown in Fig.31.
Fig.30 Reset configuration.
handbook, halfpage
MLA580
SCHMITT
TRIGGER
RESET
CIRCUITRY
RST
Fig.31 Power-on reset circuitry.
VDD
VDD
RST
10
μ
F
RRST
MLA612
P83CL781
P83CL782
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| P83CL782HDH | Low voltage 8-bit microcontrollers with UART and I2C-bus |
| P83CL782HDP | Low voltage 8-bit microcontrollers with UART and I2C-bus |
| P83CL781HDH | Low voltage 8-bit microcontrollers with UART and I2C-bus |
| P83CL882 | 80C51 Ultra Low Power ULP telephony controller |
| P83CL883T | TELX microcontrollers for CT0 handset/basestation applications |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| P83CL782HDB | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-Bit Microcontroller |
| P83CL782HDH | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low voltage 8-bit microcontrollers with UART and I2C-bus |
| P83CL782HDN | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-Bit Microcontroller |
| P83CL782HDP | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low voltage 8-bit microcontrollers with UART and I2C-bus |
| P83CL882 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:80C51 Ultra Low Power ULP telephony controller |
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