DSPIC30F3011 Microchip Technology Inc., DSPIC30F3011 Datasheet - Page 145

• Manufacturer Part Number: DSPIC30F3011
• Description: Dspic30f3010/3011 Enhanced Flash 16-bit Digital Signal Controller
• Manufacturer: Microchip Technology Inc.

20.3.1.1
The oscillator start-up circuitry is not linked to the POR
circuitry. Some crystal circuits (especially low fre-
quency crystals) will have a relatively long start-up
time. Therefore, one or more of the following conditions
is possible after the POR timer and the PWRT have
expired:
• The oscillator circuit has not begun to oscillate.
• The oscillator start-up timer has NOT expired (if a
• The PLL has not achieved a LOCK (if PLL is
If the FSCM is enabled and one of the above conditions
is true, then a clock failure trap will occur. The device
will automatically switch to the FRC oscillator and the
user can switch to the desired crystal oscillator in the
trap ISR.
20.3.1.2
If the FSCM is disabled and the Power-up Timer
(PWRT) is also disabled, then the device will exit
rapidly from Reset on power-up. If the clock source is
FRC, LPRC, EXTRC or EC, it will be active
immediately.
If the FSCM is disabled and the system clock has not
started, the device will be in a frozen state at the Reset
vector until the system clock starts. From the user’s
perspective, the device will appear to be in Reset until
a system clock is available.
20.3.2
The BOR (Brown-out Reset) module is based on an
internal voltage reference circuit. The main purpose of
the BOR module is to generate a device Reset when
a brown-out condition occurs. Brown-out conditions
are generally caused by glitches on the AC mains
(i.e., missing portions of the AC cycle waveform due
to bad power transmission lines or voltage sags due
to excessive current draw when a large inductive load
is turned on).
The BOR module allows selection of one of the
following voltage trip points:
• 2.6V-2.71V
• 4.1V-4.4V
• 4.58V-4.73V
© 2007 Microchip Technology Inc.
crystal oscillator is used).
used).
Note:
BOR: PROGRAMMABLE
BROWN-OUT RESET
The BOR voltage trip points indicated here
are nominal values provided for design
guidance only.
POR with Long Crystal Start-up Time
Operating without FSCM and PWRT
(with FSCM Enabled)
Confidential
A BOR will generate a Reset pulse which will reset the
device. The BOR will select the clock source, based on
the device Configuration bit values (FOS<1:0> and
FPR<3:0>). Furthermore, if an Oscillator mode is
selected, the BOR will activate the Oscillator Start-up
Timer (OST). The system clock is held until OST
expires. If the PLL is used, then the clock will be held
until the LOCK bit (OSCCON<5>) is ‘1’.
Concurrently, the POR time-out (T
time-out (T
Reset is released. If T
is being used, then a nominal delay of T
is applied. The total delay in this case is (T
T
The BOR status bit (RCON<1>) will be set to indicate
that a BOR has occurred. The BOR circuit, if enabled,
will continue to operate while in Sleep or Idle modes
and will reset the device should V
threshold voltage.
FIGURE 20-6:
FSCM
Note:
Note 1: External Power-on Reset circuit is
dsPIC30F3010/3011
).
2: R should be suitably chosen so as to
3: R1 should be suitably chosen so as to
PWRT
Dedicated supervisory devices, such as
the MCP1XX and MCP8XX, may also be
used as an external Power-on Reset
circuit.
required only if the V
is too slow. The diode D helps discharge
the capacitor quickly when V
down.
make sure that the voltage drop across
R does not violate the device’s electrical
specification.
limit any current flowing into MCLR from
external capacitor C, in the event of
MCLR/V
Electrostatic
Electrical Overstress (EOS).
D
V
) will be applied before the internal
DD
R
C
PP
PWRT
EXTERNAL POWER-ON
RESET CIRCUIT (FOR
SLOW V
pin breakdown due to
R1
Discharge
= 0 and a crystal oscillator
DD
DD
DD
POR
dsPIC30F
DS70141D-page 143
MCLR
fall below the BOR
POWER-UP)
power-up slope
) and the PWRT
FSCM
(ESD)
DD
powers
= 100 μs
POR
or
+