PIC16C923-04I/CL Microchip Technology, PIC16C923-04I/CL Datasheet - Page 106

• Manufacturer Part Number: PIC16C923-04I/CL
• Description: 8-Bit CMOS Microcontroller with LCD Driver
• Manufacturer: Microchip Technology

PIC16C9XX
14.3
The PIC16CXX differentiates between various kinds of
reset:
• Power-on Reset (POR)
• MCLR Reset during normal operation
• MCLR Reset during SLEEP
• WDT Reset (normal operation)
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 (POR), on the MCLR and
WDT Reset, and on MCLR Reset during SLEEP. They
are not affected by a WDT Wake-up, which is viewed as
FIGURE 14-7: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
DS30444E - page 106
Note 1: This is a separate oscillator from the RC oscillator of the CLKIN pin.
MCLR
OSC1
V
DD
2: See Table 14-3 for time-out situations.
Reset
RC OSC
On-chip
OST/PWRT
V
Module
(1)
detect
WDT
DD
rise
OST
PWRT
10-bit Ripple counter
WDT
10-bit Ripple counter
Time-out
Power-on Reset
External
Reset
SLEEP
Enable PWRT
Enable OST
the resumption of normal operation. The TO and PD
bits are set or cleared differently in different reset situ-
ations as indicated in Table 14-4. These bits are used
in software to determine the nature of the reset. See
Table 14-6 for a full description of reset states of all reg-
isters.
A simplified block diagram of the on-chip reset circuit is
shown in Figure 14-7.
The devices all 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.
(2)
(2)
1997 Microchip Technology Inc.
S
R
Q
Chip_Reset