PIC16F636-I Datasheet, PDF (133/234 Pages) Microchip Technology – 8/14-Pin, Flash-Based 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC12F635/PIC16F636/639
12.2 Reset
The PIC12F635/PIC16F636/639 differentiates between
various kinds of Reset:
a) Power-on Reset (POR)
b) Wake-up Reset (WUR)
c) WDT Reset during normal operation
d) WDT Reset during Sleep
e) MCLR Reset during normal operation
f) MCLR Reset during Sleep
g) Brown-out Reset (BOR)
Some registers are not affected in any Reset condition;
their status is unknown on POR and unchanged in any
other Reset. Most other registers are reset to a “Reset
state” on:
• Power-on Reset
• MCLR Reset
• MCLR Reset during Sleep
• WDT Reset
• Brown-out Reset
They are not affected by a WDT wake-up since this is
viewed as the resumption of normal operation. TO and
PD bits are set or cleared differently in different Reset
situations, as indicated in Table 12-3. These bits are
used in software to determine the nature of the Reset.
See Table 12-4 for a full description of Reset states of
all registers.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 12-1.
The MCLR Reset path has a noise filter to detect and
ignore small pulses. See Section 15.0 “Electrical
Specifications” for pulse width specifications.
FIGURE 12-1:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
MCLR/VPP pin
VDD
External Reset
Sleep
WDT
Module
WDT
Time-out
Reset
VDD Rise
Detect
Power-on Reset
Brown-out⁽¹⁾
Reset
BOREN ^<1>
BOREN<0>
SBOREN
OSC1/
CLKI pin
OST/PWRT
OST
10-bit Ripple Counter
PWRT
LFINTOSC
11-bit Ripple Counter
Sleep
WURE
Wake-up Interrupt
RA3 Change
S
Chip_Reset
R
Q
Note 1: Refer to the Configuration Word register (Register 12-1).
Enable PWRT
Enable OST
© 2007 Microchip Technology Inc.
DS41232D-page 131