Datasheet

PIC18F1230/1330
 2009 Microchip Technology Inc. DS39758D-page 39
5.0 RESET
The PIC18F1230/1330 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 6.1.2.4 “Stack Full and Underflow Resets”.
WDT Resets are covered in Section 20.2 “Watchdog
Timer (WDT)”.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 5-1.
5.1 RCON Register
Device Reset events are tracked through the RCON
register (Register 5-1). 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 5.6 “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 11.0 “Interrupts”. BOR is covered in
Section 5.4 “Brown-out Reset (BOR)”.
FIGURE 5-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External Reset
MCLR
VDD
OSC1
WDT
Time-out
V
DD Rise
Detect
OST/PWRT
INTRC
(1)
POR Pulse
OST
10-Bit Ripple Counter
PWRT
11-Bit Ripple Counter
Enable OST
(2)
Enable PWRT
Note 1: This is the INTRC source from the internal oscillator block and is separate from the RC oscillator of the CLKI pin.
2: See Table 5-2 for time-out situations.
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