Datasheet

PIC12F510/16F506
DS41268D-page 68 © 2007 Microchip Technology Inc.
10.7 Time-out Sequence, Power-down
and Wake-up from Sleep Status
Bits (TO
, PD, GPWUF/RBWUF)
The TO, PD and (GPWUF/RBWUF) 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.
TABLE 10-8: TO/PD/(GPWUF/RBWUF)
STATUS AFTER RESET
10.8 Reset on Brown-out
A brown-out is a condition where device power (VDD)
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 PIC12F510/16F506 devices when a brown-
out occurs, external brown-out protection circuits may
be built, as shown in Figure 10-12 and Figure 10-13.
FIGURE 10-12: BROWN-OUT
PROTECTION CIRCUIT 1
FIGURE 10-13: BROWN-OUT
PROTECTION CIRCUIT 2
FIGURE 10-14: BROWN-OUT
PROTECTION CIRCUIT 3
CWUF
GPWUF/
RBWUF
TO
PD Reset Caused By
0000WDT wake-up from
Sleep
0 0 0 u WDT time-out (not
from Sleep)
0010MCLR
wake-up from
Sleep
0 0 1 1 Power-up
00uuMCLR
not during
Sleep
0 1 1 0 Wake-up from Sleep
on pin change
1 0 1 0 Wake-up from Sleep
on comparator
change
Legend: u = unchanged
Note 1: This circuit will activate Reset when VDD goes
below Vz + 0.7V (where Vz = Zener voltage).
2: Pin must be configured as MCLR
.
33k
10k
40k
(1)
VDD
MCLR
(2)
PIC12F510
VDD
Q1
PIC16F506
Note 1: This brown-out circuit is less expensive,
although less accurate. Transistor Q1 turns
off when V
DD is below a certain level such
that:
2: Pin must be configured as MCLR
.
V
DD •
R1
R1 + R2
= 0.7V
R2
40k
(1)
VDD
MCLR
(2)
PIC12F510
R1
Q1
VDD
PIC16F506
Note: This brown-out protection circuit employs
Microchip Technology’s MCP809 microcon-
troller supervisor. There are 7 different trip
point selections to accommodate 5V to 3V
systems.
MCLR
PIC12F510
VDD
VDD
VSS
RST
MCP809
VDD
Bypass
Capacitor
PIC16F506