PIC16F676-I Datasheet, PDF (59/132 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F630/676
9.3 Reset
The PIC16F630/676 differentiates between various
kinds of Reset:
a) Power-on Reset (POR)
b) WDT Reset during normal operation
c) WDT Reset during Sleep
d) MCLR Reset during normal operation
e) MCLR Reset during Sleep
f) Brown-out Detect (BOD)
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
• WDT Reset
• WDT Reset during Sleep
• Brown-out Detect (BOD)
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 9-4. These bits are
used in software to determine the nature of the Reset.
See Table 9-7 for a full description of Reset states of all
registers.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 9-4.
The MCLR Reset path has a noise filter to detect and
ignore small pulses. See Table 12-4 in Electrical
Specifications Section for pulse-width specification.
FIGURE 9-4:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External
Reset
MCLR/
VPP pin
VDD
WDT
Module
VDD Rise
Detect
SLEEP
WDT
Time-out
Reset
Power-on Reset
Brown-out
Reset
BODEN
OSC1/
CLKIN
pin
OST/PWRT
OST
10-bit Ripple Counter
On-chip⁽¹⁾
RC OSC
PWRT
10-bit Ripple Counter
S
Q
Chip_Reset
R
Q
Enable PWRT
Enable OST
Note 1: This is a separate oscillator from the INTOSC/EC oscillator.
See Table 9-3 for time-out situations.
 2010 Microchip Technology Inc.
DS40039F-page 59