PIC16C620 Microchip Technology, PIC16C620 Datasheet - Page 50

• Manufacturer Part Number: PIC16C620
• Description: EPROM-Based 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

PIC16C62X
9.4
9.4.1
The on-chip POR circuit holds the chip in reset until
V
tion. To take advantage of the POR, just tie the MCLR
pin through a resistor to V
nal RC components usually needed to create Power-on
Reset. A maximum rise time for V
Electrical Specifications for details.
The POR circuit does not produce an internal reset
when V
When the device starts normal operation (exits the
reset condition), device operating parameters (voltage,
frequency, temperature, etc.) must be met to ensure
operation. If these conditions are not met, the device
must be held in reset until the operating conditions are
met.
For additional information, refer to Application Note
AN607 “Power-up Trouble Shooting”.
9.4.2
The Power-up Timer provides a fixed 72 ms (nominal)
time-out on power-up only, from POR or Brown-out
Reset. The Power-up Timer operates on an internal RC
oscillator. The chip is kept in reset as long as PWRT is
active. The PWRT delay allows the V
acceptable level. A configuration bit, PWRTE can
disable (if set) or enable (if cleared or programmed) the
Power-up Timer. The Power-up Timer should always be
enabled when Brown-out Reset is enabled.
FIGURE 9-8:
DS30235G-page 50
DD
has reached a high enough level for proper opera-
DD
Power-on Reset (POR), Power-up
Timer (PWRT), Oscillator Start-up
Timer (OST) and Brown-out Reset
(BOR)
POWER-ON RESET (POR)
POWER-UP TIMER (PWRT)
declines.
Internal
Internal
Internal
Reset
Reset
Reset
BROWN-OUT SITUATIONS
V
V
V
DD
DD
DD
DD
. This will eliminate exter-
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is required. See
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to rise to an
Preliminary
<72 ms
72 ms
The Power-Up Time delay will vary from chip to chip
and due to V
See DC parameters for details.
9.4.3
The Oscillator Start-Up Timer (OST) provides a 1024
oscillator cycle (from OSC1 input) delay after the
PWRT delay is over. This ensures that the crystal
oscillator or resonator has started and stabilized.
The OST time-out is invoked only for XT, LP and HS
modes and only on power-on reset or wake-up from
SLEEP.
9.4.4
The PIC16C62X members have on-chip Brown-out
Reset circuitry. A configuration bit, BOREN, can dis-
able (if clear/programmed) or enable (if set) the
Brown-out Reset circuitry. If V
to V
parameter (TBOR) in Table 12-6, the brown-out situa-
tion will reset the chip. A reset is not guaranteed to
occur if V
(TBOR).
On any reset (Power-on, Brown-out, Watchdog, etc.)
the chip will remain in Reset until V
BV
keep the chip in reset an additional 72 ms.
If V
running, the chip will go back into a Brown-out Reset
and the Power-up Timer will be re-initialized. Once V
rises above BV
72 ms reset. The Power-up Timer should always be
enabled when Brown-out Reset is enabled. Figure 9-8
shows typical Brown-out situations.
DD
72 ms
72 ms
DD
BOR
. The Power-up Timer will now be invoked and will
drops below BV
OSCILLATOR START-UP TIMER (OST)
BROWN-OUT RESET (BOR)
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parameter D005(V
falls below 4.0V for less than parameter
DD
DD
, temperature and process variation.
, the Power-Up Timer will execute a
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1998 Microchip Technology Inc.
while the Power-up Timer is
BV
BV
BV
BV
BV
BV
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BOR
DD
DD
DD
DD
DD
DD
falls below 4.0V refer
Max.
Min.
Max.
Min.
Max.
Min.
) for greater than
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rises above
DD