DSPIC30F5011_06 Datasheet, PDF (147/224 Pages) Microchip Technology – High-Performance, 16-bit Digital Signal Controllers

dsPIC30F5011/5013
20.3 Reset
The dsPIC30F5011/5013 differentiates between
various kinds of Reset:
a) Power-on Reset (POR)
b) MCLR Reset during normal operation
c) MCLR Reset during Sleep
d) Watchdog Timer (WDT) Reset (during normal
operation)
e) Programmable Brown-out Reset (BOR)
f) RESET Instruction
g) Reset caused by trap lockup (TRAPR)
h) Reset caused by illegal opcode or by using an
uninitialized W register as an address pointer
(IOPUWR)
Different registers are affected in different ways by var-
ious Reset conditions. Most registers are not affected
by a WDT wake-up since this is viewed as the resump-
tion of normal operation. Status bits from the RCON
register are set or cleared differently in different Reset
situations, as indicated in Table 20-5. These bits are
used in software to determine the nature of the Reset.
A block diagram of the On-Chip Reset Circuit is shown
in Figure 20-2.
A MCLR noise filter is provided in the MCLR Reset
path. The filter detects and ignores small pulses.
Internally generated Resets do not drive MCLR pin low.
FIGURE 20-2:
RESET SYSTEM BLOCK DIAGRAM
RESET
Instruction
MCLR
Digital
Glitch Filter
Sleep or Idle
WDT
Module
VDD Rise
Detect
POR
VDD
Brown-out
Reset
BOREN
BOR
Trap Conflict
Illegal Opcode/
Uninitialized W Register
S
R
Q
SYSRST
20.3.1 POR: POWER-ON RESET
A power-on event will generate an internal POR pulse
when a VDD rise is detected. The Reset pulse will occur
at the POR circuit threshold voltage (VPOR) which is
nominally 1.85V. The device supply voltage character-
istics must meet specified starting voltage and rise rate
requirements. The POR pulse will reset a POR timer
and place the device in the Reset state. The POR also
selects the device clock source identified by the oscil-
lator configuration fuses.
The POR circuit inserts a small delay, TPOR, which is
nominally 10 μs and ensures that the device bias cir-
cuits are stable. Furthermore, a user selected power-
up time-out (TPWRT) is applied. The TPWRT parameter
is based on device Configuration bits and can be 0 ms
(no delay), 4 ms, 16 ms or 64 ms. The total delay is at
device power-up, TPOR + TPWRT. When these delays
have expired, SYSRST will be negated on the next
leading edge of the Q1 clock and the PC will jump to the
Reset vector.
The timing for the SYSRST signal is shown in
Figure 20-3 through Figure 20-5.
© 2006 Microchip Technology Inc.
DS70116F-page 145