Datasheet

 2011-2012 Microchip Technology Inc. DS75018C-page 83
dsPIC33FJ06GS001/101A/102A/202A and dsPIC33FJ09GS302
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
Note 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 programmable 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 oper-
ation. After the delay, T
PWRT has elapsed and 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: If the Fail-Safe Clock Monitor (FSCM) is enabled, it 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 2.65V nominal
T
BOR BOR extension time 100 s maximum
T
PWRT Programmable
Power-up Time delay
0-128 ms nominal
TFSCM Fail-Safe Clock Mon-
itor delay
900 s maximum
Note: When the device exits the Reset con-
dition (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 application 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 the
specification.