
2005 Microchip Technology Inc.
Preliminary
DS41265A-page 193
PIC16F946
16.2
Reset
The PIC16F946 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 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 (BOR)
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
used in software to determine the nature of the Reset.
See
Table 16-5 for a full description of Reset states of
all registers.
A simplified block diagram of the On-Chip Reset Circuit
The MCLR Reset path has a noise filter to detect and
FIGURE 16-1:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
S
R
Q
External
Reset
MCLR/VPP pin
VDD
OSC1/
WDT
Module
VDD Rise
Detect
OST/PWRT
LFINTOSC
WDT
Time-out
Power-on Reset
OST
10-bit Ripple Counter
PWRT
Chip_Reset
11-bit Ripple Counter
Reset
Enable OST
Enable PWRT
SLEEP
Brown-out(1)
Reset
SBOREN
BOREN
CLKI pin
Note
1: