Datasheet

PIC16LF1904/6/7
DS41569A-page 50 Preliminary  2011 Microchip Technology Inc.
5.1 Power-on Reset (POR)
The POR circuit holds the device in Reset until VDD has
reached an acceptable level for minimum operation.
Slow rising V
DD, fast operating speeds or analog
performance may require greater than minimum V
DD.
The PWRT, BOR or MCLR
features can be used to
extend the start-up period until all device operation
conditions have been met.
5.1.1 POWER-UP TIMER (PWRT)
The Power-up Timer provides a nominal 64 ms
time-out on POR or Brown-out Reset.
The device is held in Reset as long as PWRT is active.
The PWRT delay allows additional time for the V
DD to
rise to an acceptable level. The Power-up Timer is
enabled by clearing the PWRTE bit in Configuration
Word 1.
The Power-up Timer starts after the release of the POR
and BOR.
For additional information, refer to Application Note
AN607, “Power-up Trouble Shooting” (DS00607).
5.2 Brown-Out Reset (BOR)
The BOR circuit holds the device in Reset when VDD
reaches a selectable minimum level. Between the
POR and BOR, complete voltage range coverage for
execution protection can be implemented.
The Brown-out Reset module has four operating
modes controlled by the BOREN<1:0> bits in Configu-
ration Word 1. The four operating modes are:
• BOR is always on
• BOR is off when in Sleep
• BOR is controlled by software
• BOR is always off
Refer to Table 5-1 for more information.
The Brown-out Reset voltage level is selectable by
configuring the BORV bit in Configuration Word 2.
A V
DD noise rejection filter prevents the BOR from trig-
gering on small events. If V
DD falls below VBOR for a
duration greater than parameter T
BORDC, the device
will reset. See Figure 5-2 for more information.
TABLE 5-1: BOR OPERATING MODES
5.2.1 BOR IS ALWAYS ON
When the BOREN bits of Configuration Word 1 are set
to ‘11’, the BOR is always on. The device start-up will
be delayed until the BOR is ready and V
DD is higher
than the BOR threshold.
BOR protection is active during Sleep. The BOR does
not delay wake-up from Sleep.
5.2.2 BOR IS OFF IN SLEEP
When the BOREN bits of Configuration Word 1 are set
to ‘10’, the BOR is on, except in Sleep. The device
start-up will be delayed until the BOR is ready and VDD
is higher than the BOR threshold.
BOR protection is not active during Sleep. The device
wake-up will be delayed until the BOR is ready.
5.2.3 BOR CONTROLLED BY SOFTWARE
When the BOREN bits of Configuration Word 1 are set
to ‘01’, the BOR is controlled by the SBOREN bit of the
BORCON register. The device start-up is not delayed
by the BOR ready condition or the V
DD level.
BOR protection begins as soon as the BOR circuit is
ready. The status of the BOR circuit is reflected in the
BORRDY bit of the BORCON register.
BOR protection is unchanged by Sleep.
BOREN<1:0> SBOREN Device Mode BOR Mode
Device Operation
upon release of POR
Device Operation
upon wake- up from
Sleep
11 X X Active Waits for BOR ready
(1)
10 X
Awake Active
Waits for BOR ready
Sleep Disabled
01
1
X
Active Begins immediately
0 Disabled Begins immediately
00 X X Disabled Begins immediately
Note 1: Even though this case specifically waits for the BOR, the BOR is already operating, so there is no delay in
start-up.