Datasheet

 2009-2011 Microchip Technology Inc. DS41365E-page 245
PIC18(L)F1XK22
21.0 RESET
The PIC18(L)F1XK22 devices differentiate between var-
ious 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 3.1.2.4 “Stack Overflow and Underflow
Resets”. WDT Resets are covered in Section 22.2
“Watchdog Timer (WDT)”.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 21-1.
21.1 RCON Register
Device Reset events are tracked through the RCON
register (Register 21-1). The lower five bits of the reg-
ister 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 21.6 “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 7.0 “Interrupts”. BOR is covered in
Section 21.4 “Brown-out Reset (BOR)”.
FIGURE 21-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External Reset
MCLR
VDD
OSC1
WDT
Time-out
V
DD Rise
Detect
OST/PWRT
LFINTOSC
POR Pulse
OST
(2)
10-bit Ripple Counter
PWRT
(2)
11-bit Ripple Counter
Enable OST
(1)
Enable PWRT
Note 1: See Table 21-2 for time-out situations.
2: PWRT and OST counters are reset by POR and BOR. See Sections 21.3 and 21.4.
Brown-out
Reset
BOREN
RESET
Instruction
Stack
Pointer
Stack Full/Underflow Reset
Sleep
( )_IDLE
1024 Cycles
65.5 ms
32 s
MCLRE
S
R
Q
Chip_Reset