PIC16C505T-04/SL View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'PIC16C505T-04/SL' PDF : 85 Pages View PDF
PIC16C505
7.7 Time-Out Sequence, Power Down,
and Wake-up from SLEEP Status Bits
(TO/PD/RBWUF)
The TO, PD, and 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 7-7: TO/PD/RBWUF STATUS
AFTER RESET
RBWUF TO PD
RESET caused by
0
0 0 WDT wake-up from
SLEEP
0
0 u WDT time-out (not from
SLEEP)
0
1 0 MCLR wake-up from
SLEEP
0
1 1 Power-up
0
u u MCLR not during SLEEP
1
1 0 Wake-up from SLEEP on
pin change
Legend:
Note 1:
u = unchanged
The TO, PD, and RBWUF bits maintain their
status (u) until a reset occurs. A low-pulse on the
MCLR input does not change the TO, PD, and
RBWUF status bits.
7.8 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 PIC16C505 devices when a brown-out
occurs, external brown-out protection circuits may be
built, as shown in Figure 7-12 and Figure 7-13.
FIGURE 7-12: BROWN-OUT PROTECTION
CIRCUIT 1
VDD
33k
10k
VDD
PIC16C505
Q1 MCLR(1)
40k*
FIGURE 7-13: BROWN-OUT PROTECTION
CIRCUIT 2
VDD
VDD
R1
PIC16C505
Q1 MCLR(1)
R2
40k*
This brown-out circuit is less expensive, although
less accurate. Transistor Q1 turns off when VDD
is below a certain level such that:
VDD •
R1 = 0.7V
R1 + R2
Note 1: Pin must be confirmed as MCLR.
FIGURE 7-14: BROWN-OUT PROTECTION
CIRCUIT 3
VDD
MCP809 bypass
VSS
capacitor
VDD
RST
VDD
MCLR
PIC12C5XX
This brown-out protection circuit employs Microchip
Technology’s MCP809 microcontroller supervisor.
There are 7 different trip point selections to
accommodate 5V to 3V systems.
This circuit will activate reset when VDD goes below
Vz + 0.7V (where Vz = Zener voltage).
Note 1: Pin must be confirmed as MCLR.
DS40192C-page 36
© 1999 Microchip Technology Inc.
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