PIC18F23K22 Datasheet, PDF (59/492 Pages) Microchip Technology – 28/40/44-Pin, Low-Power, High-Performance Microcontrollers with nanoWatt XLP Technology

PIC18(L)F2X/4XK22
4.0 RESET
The PIC18(L)F2X/4XK22 devices differentiate between
various kinds of Reset:
a) Power-on Reset (POR)
b) MCLR Reset during normal operation
c) MCLR Reset during power-managed modes
d) Watchdog Timer (WDT) Reset (during
execution)
e) Programmable Brown-out Reset (BOR)
f) RESET Instruction
g) Stack Full Reset
h) Stack Underflow Reset
This section discusses Resets generated by MCLR,
POR and BOR and covers the operation of the various
start-up timers. Stack Reset events are covered in
Section 5.1.2.4 “Stack Full and Underflow Resets”.
WDT Resets are covered in Section 24.2 “Watchdog
Timer (WDT)”.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 4-1.
4.1 RCON Register
Device Reset events are tracked through the RCON
register (Register 4-1). The lower five bits of the
register indicate that a specific Reset event has
occurred. In most cases, these bits can only be cleared
by the event and must be set by the application after
the event. The state of these flag bits, taken together,
can be read to indicate the type of Reset that just
occurred. This is described in more detail in
Section 4.6 “Reset State of Registers”.
The RCON register also has control bits for setting
interrupt priority (IPEN) and software control of the
BOR (SBOREN). Interrupt priority is discussed in
Section 9.0 “Interrupts”. BOR is covered in
Section 4.4 “Brown-out Reset (BOR)”.
FIGURE 4-1:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
RESET
Instruction
Stack
Pointer
Stack Full/Underflow Reset
MCLR
External Reset
MCLRE
( )_IDLE
Sleep
WDT
Time-out
VDD
Detect
POR
VDD
Brown-out
Reset
BOREN
S
OST/PWRT
OST^{(2) 1024 Cycles}
10-bit Ripple Counter
R
OSC1
Chip_Reset
Q
32 s
LFINTOSC
PWRT⁽²⁾ 65.5 ms
11-bit Ripple Counter
Note 1: See Table for time-out situations.
2: PWRT and OST counters are reset by POR and BOR. See Sections 4.3 and 4.4.
Enable PWRT
Enable OST⁽¹⁾
 2010 Microchip Technology Inc.
Preliminary
DS41412B-page 59