PIC16F688 Datasheet, PDF (104/174 Pages) Microchip Technology – 14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F688
11.3 Reset
The PIC16F688 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
• MCLR Reset during Sleep
• WDT Reset
• 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 11-2. These bits are
used in software to determine the nature of the Reset.
See Table 11-4 for a full description of Reset states of
all registers.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 11-1.
The MCLR Reset path has a noise filter to detect and
ignore small pulses. See Section 14.0 “Electrical
Specifications” for pulse width specifications.
FIGURE 11-1:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External
Reset
MCLR/VPP pin
VDD
SLEEP
WDT
Module
WDT
Time-out
Reset
VDD Rise
Detect
Power-on Reset
Brown-out⁽¹⁾
Detect
BODEN
SBODEN
OSC1/
CLKI pin
OST/PWRT
OST
10-bit Ripple Counter
PWRT
LFINTOSC
11-bit Ripple Counter
S
Chip_Reset
R
Q
Note 1: Refer to the Configuration Word register (Register 11-1).
Enable PWRT
Enable OST
DS41203B-page 102
Preliminary
 2004 Microchip Technology Inc.