Datasheet

 2011-2012 Microchip Technology Inc. DS70652E-page 91
dsPIC33FJ16(GP/MC)101/102 AND dsPIC33FJ32(GP/MC)101/102/104
FIGURE 6-2: SYSTEM RESET TIMING
Reset
Run
Device Status
V
DD
VPOR
VBOR
POR
BOR
SYSRST
TPWRT
TPOR
TBOR
Oscillator Clock
T
OSCD TOST TLOCK
Time
FSCM
T
FSCM
1
2
3
4
5
6
1. POR: A POR circuit holds the device in Reset when the power supply is turned on. The POR circuit is active until V
DD crosses the
V
POR threshold and the delay, TPOR, has elapsed.
2. BOR: The on-chip voltage regulator has a BOR circuit that keeps the device in Reset until V
DD crosses the VBOR threshold and the
delay, T
BOR, has elapsed. The delay, TBOR, ensures the voltage regulator output becomes stable.
3. PWRT Timer: The Power-up Timer continues to hold the processor in Reset for a specific period of time (T
PWRT) after a BOR. The
delay, T
PWRT, ensures that the system power supplies have stabilized at the appropriate level for full-speed operation. After the delay,
T
PWRT, has elapsed, the SYSRST becomes inactive, which in turn, enables the selected oscillator to start generating clock cycles.
4. Oscillator Delay: The total delay for the clock to be ready for various clock source selections is given in Table 6-1. Refer to
Section 8.0 “Oscillator Configuration” for more information.
5. When the oscillator clock is ready, the processor begins execution from location, 0x000000. The user application programs a GOTO
instruction at the Reset address, which redirects program execution to the appropriate start-up routine.
6. The Fail-Safe Clock Monitor (FSCM), if enabled, begins to monitor the system clock when the system clock is ready and the delay,
T
FSCM, has elapsed.
TABLE 6-2: OSCILLATOR PARAMETERS
Symbol Parameter Value
V
POR POR Threshold 1.8V nominal
T
POR POR Extension Time 30 s maximum
V
BOR BOR Threshold 2.5V nominal
T
BOR BOR Extension Time 100 s maximum
T
PWRT Power-up Time
Delay
64 ms nominal
TFSCM Fail-Safe Clock
Monitor Delay
900 s maximum
Note: When the device exits the Reset condition
(begins normal operation), the device
operating parameters (voltage, frequency,
temperature, etc.) must be within their
operating ranges; otherwise, the device
may not function correctly. The user appli-
cation must ensure that the delay between
the time power is first applied, and the time
SYSRST
becomes inactive, is long
enough to get all operating parameters
within specification.