DSPIC30F6012A Microchip Technology Inc., DSPIC30F6012A Datasheet - Page 157

• Manufacturer Part Number: DSPIC30F6012A
• Description: Dspic30f6011a/6012a/6013a/6014a High-performance Digital Signal Controllers
• Manufacturer: Microchip Technology Inc.

FIGURE 20-5:
20.4.1.1
The oscillator start-up circuitry is not linked to the POR
circuitry. Some crystal circuits (especially low frequency
crystals) will have a relatively long start-up time. There-
fore, 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
• 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.
20.4.1.2
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.
© 2006 Microchip Technology Inc.
a crystal oscillator is used).
used).
PWRT Time-out
OST Time-out
Internal POR
Internal Reset
POR with Long Crystal Start-up
Time (with FSCM Enabled)
Operating without FSCM and PWRT
MCLR
V
DD
TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO V
dsPIC30F6011A/6012A/6013A/6014A
T
OST
Preliminary
T
PWRT
20.4.2
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 exces-
sive 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
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<2:0> and
FPR<4:0>). 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’.
Note:
BOR: PROGRAMMABLE
BROWN-OUT RESET
The BOR voltage trip points indicated here
are nominal values provided for design
guidance only.
DD
DS70143C-page 155
): CASE 2