PIC17C752 MICROCHIP [Microchip Technology], PIC17C752 Datasheet - Page 21

• Manufacturer Part Number: PIC17C752
• Description: High-Performance 8-Bit CMOS EPROM Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

5.0
The PIC17CXXX differentiates between various kinds
of reset:
• Power-on Reset (POR)
• MCLR reset during normal operation
• Brown-out Reset
• 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 forced to a “reset
state” on Power-on Reset (POR), Brown-out Reset
(BOR), on MCLR or WDT Reset and on MCLR reset
during SLEEP. A WDT Reset during SLEEP, is viewed
as the resumption of normal operation. The TO and PD
bits are set or cleared differently in different reset situ-
ations as indicated in Table 5-3. These bits are used in
software to determine the nature of the reset. See
Table 5-4 for a full description of reset states of all reg-
isters.
FIGURE 5-1:
1997 Microchip Technology Inc.
MCLR
OSC1
† This RC oscillator is shared with the WDT
V
DD
when not in a power-up sequence.
RESET
RC OSC†
OST/PWRT
On-chip
V
Module
Module
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
detect
WDT
DD
BOR
rise
OST
PWRT
10-bit Ripple counter
10-bit Ripple counter
Brown-out
Power_On_Reset
Reset
Time_Out
Reset
WDT
External
Reset
Preliminary
A simplified block diagram of the on-chip reset circuit is
shown in Figure 5-1.
Note:
Power_Up
(Enable the PWRT timer
only during Power_Up)
(Power_Up) + (Wake_Up) (XT + LF)
(Enable the OST if it is Power_Up or Wake_Up
from SLEEP and OSC type is XT or LF)
While the device is in a reset state, the
internal phase clock is held in the Q1 state.
Any processor mode that allows external
execution will force the RE0/ALE pin as a
low output and the RE1/OE and RE2/WR
pins as high outputs.
S
R
DS30264A-page 21
Q
Chip_Reset