
2002 Microchip Technology Inc.
DS41120B-page 121
PIC16C717/770/771
12.3
RESET
The PIC16C717/770/771 devices have several differ-
ent RESETS. These RESETS are grouped into two
classifications; power-up and non-power-up. The
power-up type RESETS are the Power-on and Brown-
out Resets which assume the device VDD was below its
normal operating range for the device’s configuration.
The non power-up type RESETS assume normal oper-
ating limits were maintained before/during and after the
RESET.
Power-on Reset (POR)
Programmable Brown-out Reset (PBOR)
MCLR Reset during normal operation
MCLR Reset during SLEEP
WDT Reset (during normal operation)
Some registers are not affected in any RESET condi-
tion. Their status is unknown on a Power-up Reset and
unchanged in any other RESET. Most other registers
are placed into an initialized state upon RESET, how-
ever they are not affected by a WDT Reset during
SLEEP, because this is considered a WDT Wake-up,
which is viewed as the resumption of normal operation.
Several status bits have been provided to indicate
which
RESET
occurred
(see
See
Table 12-6 for a full description of RESET states of all
registers.
A simplified block diagram of the On-Chip Reset circuit
These devices have a MCLR noise filter in the MCLR
Reset path. The filter will detect and ignore small
pulses.
It should be noted that a WDT Reset does not drive
MCLR pin low.
FIGURE 12-4:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
S
R
Q
External
RESET
MCLR
VDD
OSC1
WDT
Module
VDD rise
detect
OST/PWRT
Dedicated
Oscillator
Power-on Reset
OST
10-bit Ripple counter
PWRT
Chip_Reset
10-bit Ripple counter
Enable OST
Enable PWRT
SLEEP
Brown-out
Programmable
BODEN
Time-out