PIC16F631/677/685/687/689/690
On any Reset (Power-on, Brown-out Reset, Watchdog
Timer, etc.), the chip will remain in Reset until VDD rises
above VBOR (see Figure 14-3). The Power-up Timer
will now be invoked, if enabled and will keep the chip in
Reset an additional 64 ms.
14.2.4
BROWN-OUT RESET (BOR)
The BOREN0 and BOREN1 bits in the Configuration
Word register select one of four BOR modes. Two
modes have been added to allow software or hardware
control of the BOR enable. When BOREN<1:0> = 01,
the SBOREN bit (PCON<4>) enables/disables the
BOR allowing it to be controlled in software. By
selecting BOREN<1:0>, the BOR is automatically
disabled in Sleep to conserve power and enabled on
wake-up. In this mode, the SBOREN bit is disabled.
See Register 14-2 for the Configuration Word
definition.
Note:
The Power-up Timer is enabled by the
PWRTE bit in the Configuration Word
register.
If VDD drops below VBOR while the Power-up Timer is
running, the chip will go back into a Brown-out Reset
and the Power-up Timer will be re-initialized. Once VDD
rises above VBOR, the Power-up Timer will execute a
64 ms Reset.
If VDD falls below VBOR for greater than parameter
(TBOR) (see Section 17.0 “Electrical Specifications”),
the Brown-out situation will reset the device. This will
occur regardless of VDD slew rate. A Reset is not insured
to occur if VDD falls below VBOR for less than parameter
(TBOR).
FIGURE 14-3:
BROWN-OUT SITUATIONS
VDD
VBOR
Internal
Reset
(1)
64 ms
VDD
VBOR
Internal
Reset
< 64 ms
(1)
64 ms
VDD
VBOR
Internal
Reset
(1)
64 ms
Note 1: 64 ms delay only if PWRTE bit is programmed to ‘0’.
DS41262D-page 198
© 2007 Microchip Technology Inc.
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