PIC12C508A Microchip Technology, PIC12C508A Datasheet - Page 44

• Manufacturer Part Number: PIC12C508A
• Description: 8-Pin/ 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

PIC12C5XX
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.
TABLE 8-7:
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 PIC12C5XX devices when a brown-out
occurs, external brown-out protection circuits may be
built, as shown in Figure 8-13 , Figure 8-14 and
Figure 8-15
FIGURE 8-13: BROWN-OUT PROTECTION
DS40139E-page 44
GPWUF TO
Legend: u = unchanged
Note 1: The TO, PD, and GPWUF bits maintain
This circuit will activate reset when V
Vz + 0.7V (where Vz = Zener voltage).
*Refer to Figure 8-7 and Table 11-1 for internal
weak pull-up on MCLR.
0
0
0
0
0
1
33k
V
Time-Out Sequence, Power Down,
and Wake-up from SLEEP Status Bits
(TO/PD/GPWUF)
Reset on Brown-Out
their status (u) until a reset occurs. A low-
pulse on the MCLR input does not change
the TO, PD, and GPWUF status bits.
DD
0
0
1
1
u
1
10k
PD
TO/PD/GPWUF STATUS
AFTER RESET
CIRCUIT 1
0
u
0
1
u
0
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
Q1
40k*
V
DD
RESET caused by
PIC12C5XX
V
DD
MCLR
DD
goes below
DD
)
FIGURE 8-14: BROWN-OUT PROTECTION
FIGURE 8-15: BROWN-OUT PROTECTION
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 11-1 for internal
weak pull-up on MCLR.
This
Microchip Technology’s MCP809 microcontroller
supervisor. The MCP8XX and MCP1XX family of
supervisors provide push-pull and open collector
outputs with both high and low active reset pins.
There are 7 different trip point selections to
accomodate 5V and 3V systems.
Vss
MCP809
RST
brown-out
R1
R2
V
DD
V
V
V
DD
DD
DD
CIRCUIT 2
CIRCUIT 3
capacitor
•
bypass
protection
R1 + R2
1999 Microchip Technology Inc.
R1
Q1
40k*
V
DD
= 0.7V
V
PIC12C5XX
V
PIC12C5XX
circuit
DD
DD
MCLR
MCLR
employs
DD