PIC12C672 MICROCHIP [Microchip Technology], PIC12C672 Datasheet - Page 38

• Manufacturer Part Number: PIC12C672
• Description: 8-Pin, 8-Bit CMOS Microcontroller with EEPROM Data Memory
• Manufacturer: MICROCHIP [Microchip Technology]

PIC12CE5XX
8.7
The TO, PD, and GPWUF bits in the STATUS register
can be tested to determine if a RESET condition has
been caused by a power-up condition, a MCLR or
Watchdog Timer (WDT) reset, or a MCLR or WDT
reset.
These STATUS bits are only affected by events listed
in Table 8-8.
TABLE 8-8:
Table 8-4 lists the reset conditions for the special
function registers, while Table 8-3 lists the reset
conditions for all the registers.
DS40172A-page 38
TABLE 8-7:
Legend:
Power-up
WDT Time-out
SLEEP instruction
CLRWDT
instruction
Wake-up from
SLEEP on pin
change
Legend: u = unchanged
A WDT time-out will occur regardless of the status of the
TO bit. A SLEEP instruction will be executed, regardless of
the status of the PD bit. Table 8-7 reflects the status of TO
and PD after the corresponding event.
GPWUF TO
0
0
0
0
0
1
Event
Time-Out Sequence, Power Down,
and Wake-up from SLEEP Status Bits
(TO/PD/GPWUF)
Legend: u = unchanged
Note 1: The TO, PD, and GPWUF bits main-
0
0
1
1
u
1
PD
TO/PD/GPWUF STATUS
AFTER RESET
EVENTS AFFECTING TO/PD
STATUS BITS
0
1
0
1
u
0
tain their status (u) until a reset
occurs. A low-pulse on the MCLR
input does not change the TO, PD,
and GPWUF status bits.
GPWUF TO
WDT wake-up from
SLEEP
WDT time-out (not from
SLEEP)
MCLR wake-up from
SLEEP
Power-up
MCLR not during SLEEP
Wake-up from SLEEP on
pin change
0
0
u
u
1
RESET caused by
1
0
1
1
1
PD
1
u
0
1
0
Remarks
No effect
on PD
Preliminary
8.8
A brown-out is a condition where device power (V
dips below its minimum value, but not to zero, and then
recovers. The device should be reset in the event of a
brown-out.
To reset PIC12CE5XX devices when a brown-out
occurs, external brown-out protection circuits may be
built, as shown in Figure 8-13 and Figure 8-14.
FIGURE 8-13: BROWN-OUT PROTECTION
FIGURE 8-14: BROWN-OUT PROTECTION
This circuit will activate reset when V
0.7V (where Vz = Zener voltage).
*Refer to Figure 8-7 and Table 11-7 for internal weak pull-
up on MCLR.
This brown-out circuit is less expensive, although
less accurate. Transistor Q1 turns off when V
is below a certain level such that:
*Refer to Figure 8-7 and Table 11-7 for internal weak
pull-up on MCLR.
33k
V
Reset on Brown-Out
DD
R1
R2
V
DD
V
10k
DD
CIRCUIT 1
CIRCUIT 2
•
R1 + R2
Q1
40k*
1997 Microchip Technology Inc.
R1
Q1
40k
PIC12CE5XX
MCLR
V
DD
= 0.7V
DD
PIC12CE5XX
MCLR
V
DD
goes below Vz +
DD
DD
)