Datasheet

 2010-2011 Microchip Technology Inc. DS39996F-page 93
PIC24FJ128GA310 FAMILY
TABLE 7-1: RESET FLAG BIT OPERATION
7.1 Special Function Register Reset
States
Most of the Special Function Registers (SFRs) associ-
ated with the PIC24F CPU and peripherals are reset to a
particular value at a device Reset. The SFRs are
grouped by their peripheral or CPU function and their
Reset values are specified in each section of this manual.
The Reset value for each SFR does not depend on the
type of Reset, with the exception of four registers. The
Reset value for the Reset Control register, RCON, will
depend on the type of device Reset. The Reset value
for the Oscillator Control register, OSCCON, will
depend on the type of Reset and the programmed
values of the FNOSC bits in Flash Configuration
Word 2 (CW2) (see Table 7-2). The RCFGCAL and
NVMCON registers are only affected by a POR.
7.2 Device Reset Times
The Reset times for various types of device Reset are
summarized in Ta bl e 7 -3 . Note that the system Reset
signal, SYSRST, is released after the POR delay time
expires.
The time at which the device actually begins to execute
code will also depend on the system oscillator delays,
which include the Oscillator Start-up Timer (OST) and
the PLL lock time. The OST and PLL lock times occur
in parallel with the applicable SYSRST
delay times.
The Fail-Safe Clock Monitor (FSCM) delay determines
the time at which the FSCM begins to monitor the
system clock source after the SYSRST
signal is
released.
7.3 Brown-out Reset (BOR)
PIC24FJ128GA310 family devices implement a BOR
circuit that provides the user with several configuration
and power-saving options. The BOR is controlled by
the BOREN (CW3<12>) Configuration bit.
When BOR is enabled, any drop of V
DD below the BOR
threshold results in a device BOR. Threshold levels are
described in Section 32.1 “DC Characteristics”
(Parameter DC17).
7.4 Clock Source Selection at Reset
If clock switching is enabled, the system clock source
at device Reset is chosen, as shown in Table 7-2. If
clock switching is disabled, the system clock source is
always selected according to the Oscillator Configura-
tion bits. Refer to the “PIC24F Family Reference
Manual”, Section 6.0 “Oscillator” (DS39700) for
further details.
TABLE 7-2: OSCILLATOR SELECTION vs.
TYPE OF RESET (CLOCK
SWITCHING ENABLED)
Flag Bit Setting Event Clearing Event
TRAPR (RCON<15>) Trap Conflict Event POR
IOPUWR (RCON<14>) Illegal Opcode or Uninitialized W Register Access POR
CM (RCON<9>) Configuration Mismatch Reset POR
EXTR (RCON<7>) MCLR
Reset POR
SWR (RCON<6>) RESET Instruction POR
WDTO (RCON<4>) WDT Time-out CLRWDT, PWRSAV
Instruction, POR
SLEEP (RCON<3>) PWRSAV #0 Instruction POR
DPSLP (RCON<10>) PWRSAV #0 Instruction while DSEN bit set POR
IDLE (RCON<2>) PWRSAV #1 Instruction POR
BOR (RCON<1>) POR, BOR —
POR (RCON<0>) POR —
Note: All Reset flag bits may be set or cleared by the user software.
Reset Type Clock Source Determinant
POR
FNOSC Configuration bits
(CW2<10:8>)
BOR
MCLR
COSC Control bits
(OSCCON<14:12>)
WDTO
SWR