PIC16CR58A-04I/SO View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'PIC16CR58A-04I/SO' PDF : 217 Pages View PDF
7.7 Time-Out Sequence and Power Down
Status Bits (TO/PD)
The TO and PD 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 wake-up reset.
TABLE 7-6: TO/PD STATUS AFTER
RESET
TO PD
RESET was caused by
1
1 Power-up (POR)
u
u MCLR reset (normal operation)(1)
1
0 MCLR wake-up reset (from SLEEP)
0
1 WDT reset (normal operation)
0
0 WDT wake-up reset (from SLEEP)
Legend:
Note 1:
u = unchanged
The TO and PD bits maintain their status (u) until
a reset occurs. A low-pulse on the MCLR input
does not change the TO and PD status bits.
These STATUS bits are only affected by events listed
in Table 7-7.
TABLE 7-7: EVENTS AFFECTING TO/PD
STATUS BITS
Event
TO PD
Remarks
Power-up
11
WDT Time-out
SLEEP instruction
0 u No effect on PD
10
CLRWDT instruction
11
Legend: u = unchanged
Note:
A WDT time-out will occur regardless of
the status of the TO bit. A SLEEP instruc-
tion will be executed, regardless of the sta-
tus of the PD bit.
Table 7-3 lists the reset conditions for the special
function registers, while Table 7-4 lists the reset
conditions for all the registers.
PIC16C5X
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 PIC16C5X devices when a brown-out occurs,
external brown-out protection circuits may be built, as
shown in Figure 7-14 and Figure 7-15.
FIGURE 7-14: BROWN-OUT PROTECTION
CIRCUIT 1
VDD
33k
10k
VDD
Q1
MCLR
40k PIC16C5X
This circuit will activate reset when VDD goes below Vz +
0.7V (where Vz = Zener voltage).
FIGURE 7-15: BROWN-OUT PROTECTION
CIRCUIT 2
VDD
VDD
R1
Q1
MCLR
R2
40k PIC16C5X
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
© 1998 Microchip Technology Inc.
Preliminary
DS30453B-page 41
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