16F876 Microchip Technology, 16F876 Datasheet - Page 125

• Manufacturer Part Number: 16F876
• Description: 28/40-pin 8-Bit CMOS FLASH Microcontrollers
• Manufacturer: Microchip Technology

12.3
The PIC16F87X differentiates between various kinds of
reset:
• Power-on Reset (POR)
• MCLR reset during normal operation
• MCLR reset during SLEEP
• WDT Reset (during normal operation)
• WDT Wake-up (during SLEEP)
• 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 (POR), on the MCLR and
FIGURE 12-4: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
1999 Microchip Technology Inc.
MCLR
Note 1: This is a separate oscillator from the RC oscillator of the CLKIN pin.
OSC1
V
DD
Reset
On-chip
RC OSC
OST/PWRT
Brown-out
(1)
V
Module
detect
WDT
DD
Reset
rise
OST
PWRT
WDT
Time-out
Reset
10-bit Ripple counter
10-bit Ripple counter
BODEN
Power-on Reset
External
Reset
SLEEP
Enable PWRT
Enable OST
WDT Reset, on MCLR reset during SLEEP, and Brown-
out Reset (BOR). They are not affected by a WDT
Wake-up, which is viewed as the resumption of normal
operation. The TO and PD bits are set or cleared differ-
ently in different reset situations as indicated in
Table 12-4. These bits are used in software to deter-
mine the nature of the reset. See Table 12-6 for a full
description of reset states of all registers.
A simplified block diagram of the on-chip reset circuit is
shown in Figure 12-4.
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.
PIC16F87X
S
R
DS30292B-page 125
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Chip_Reset