PIC16LC74AT-10I/SO View Datasheet(PDF) - Microchip Technology
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PIC16LC74AT-10I/SO Datasheet PDF : 288 Pages
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PIC16C7X
14.4.5 TIME-OUT SEQUENCE
On power-up the time-out sequence is as follows: First
PWRT time-out is invoked after the POR time delay has
expired. Then OST is activated. The total time-out will
vary based on oscillator configuration and the status of
the PWRT. For example, in RC mode with the PWRT
disabled, there will be no time-out at all. Figure 14-10,
Figure 14-11, and Figure 14-12 depict time-out
sequences on power-up.
Since the time-outs occur from the POR pulse, if MCLR
is kept low long enough, the time-outs will expire. Then
bringing MCLR high will begin execution immediately
(Figure 14-11). This is useful for testing purposes or to
synchronize more than one PIC16CXX device operat-
ing in parallel.
Table 14-7 shows the reset conditions for some special
function registers, while Table 14-8 shows the reset
conditions for all the registers.
14.4.6
POWER CONTROL/STATUS REGISTER
(PCON)
Applicable Devices
72 73 73A 74 74A 76 77
The Power Control/Status Register, PCON has up to
two bits, depending upon the device. Bit0 is not imple-
mented on the PIC16C73 or PIC16C74.
Bit0 is Brown-out Reset Status bit, BOR. Bit BOR is
unknown on a Power-on Reset. It must then be set by
the user and checked on subsequent resets to see if bit
BOR cleared, indicating a BOR occurred. The BOR bit
is a "Don’t Care" bit and is not necessarily predictable
if the Brown-out Reset circuitry is disabled (by clearing
bit BODEN in the Configuration Word).
Bit1 is POR (Power-on Reset Status bit). It is cleared
on a Power-on Reset and unaffected otherwise. The
user must set this bit following a Power-on Reset.
TABLE 14-3: TIME-OUT IN VARIOUS SITUATIONS, PIC16C73/74
Oscillator Configuration
XT, HS, LP
RC
Power-up
PWRTE = 1
72 ms + 1024TOSC
72 ms
PWRTE = 0
1024TOSC
—
Wake-up from SLEEP
1024 TOSC
—
TABLE 14-4: TIME-OUT IN VARIOUS SITUATIONS, PIC16C72/73A/74A/76/77
Oscillator Configuration
XT, HS, LP
RC
Power-up
PWRTE = 0
PWRTE = 1
72 ms + 1024TOSC 1024TOSC
72 ms
—
Brown-out
72 ms + 1024TOSC
72 ms
TABLE 14-5: STATUS BITS AND THEIR SIGNIFICANCE, PIC16C73/74
Wake-up from SLEEP
1024TOSC
—
POR
TO
PD
0
1
1
0
0
x
0
x
0
1
0
1
1
0
0
1
u
u
1
1
0
Legend: u = unchanged, x = unknown
Power-on Reset
Illegal, TO is set on POR
Illegal, PD is set on POR
WDT Reset
WDT Wake-up
MCLR Reset during normal operation
MCLR Reset during SLEEP or interrupt wake-up from SLEEP
© 1997 Microchip Technology Inc.
DS30390E-page 135
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