PIC18F4550-I/PT Microchip Technology Inc., PIC18F4550-I/PT Datasheet - Page 48

• Manufacturer Part Number: PIC18F4550-I/PT
• Description: 44 PIN, 32 KB FLASH, 2048 RAM, FS-USB 2.0
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4550-I/PT

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 12 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 34
• Interface: I2C/SPI/UART/USART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2455/2550/4455/4550
4.4
PIC18F2455/2550/4455/4550 devices implement a
BOR circuit that provides the user with a number of
configuration and power-saving options. The BOR
is
BOREN1:BOREN0 Configuration bits. There are a total
of four BOR configurations which are summarized in
Table 4-1.
The BOR threshold is set by the BORV1:BORV0 bits. If
BOR is enabled (any values of BOREN1:BOREN0
except ‘00’), any drop of V
D005, Section
greater than T
reset the device. A Reset may or may not occur if V
falls below V
remain in Brown-out Reset until V
If the Power-up Timer is enabled, it will be invoked after
V
Reset
(parameter 33, Table 28-12). If V
while the Power-up Timer is running, the chip will go
back into a Brown-out Reset and the Power-up Timer
will be initialized. Once V
Power-up Timer will execute the additional time delay.
BOR
independently configured. Enabling BOR Reset does
not automatically enable the PWRT.
4.4.1
When BOREN1:BOREN0 = 01, the BOR can be
enabled or disabled by the user in software. This is
done with the control bit, SBOREN (RCON<6>).
Setting SBOREN enables the BOR to function as
previously described. Clearing SBOREN disables the
BOR entirely. The SBOREN bit operates only in this
mode; otherwise, it is read as ‘0’.
TABLE 4-1:
DS39632C-page 46
DD
BOREN1
BOR Configuration
controlled
rises above V
0
0
1
1
and
for
Brown-out Reset (BOR)
SOFTWARE ENABLED BOR
BOR
an
the
BOR
BOREN0
BOR CONFIGURATIONS
by
28.1 “DC Characteristics”) for
for less than T
additional
Power-on
BOR
0
1
0
1
(parameter 35, Table 28-12) will
; it then will keep the chip in
the
DD
DD
(RCON<6>)
Unavailable
Unavailable
Unavailable
SBOREN
below V
Available
BORV1:BORV0
Status of
rises above V
time
Timer
DD
DD
BOR
rises above V
drops below V
delay,
BOR
. The chip will
(PWRT)
(parameter
BOR disabled; must be enabled by reprogramming the Configuration bits.
BOR enabled in software; operation controlled by SBOREN.
BOR enabled in hardware in Run and Idle modes, disabled during Sleep
mode.
BOR enabled in hardware; must be disabled by reprogramming the
Configuration bits.
BOR
T
PWRT
BOR
, the
and
BOR
Preliminary
are
DD
.
Placing the BOR under software control gives the user
the additional flexibility of tailoring the application to its
environment without having to reprogram the device to
change BOR configuration. It also allows the user to
tailor device power consumption in software by elimi-
nating the incremental current that the BOR consumes.
While the BOR current is typically very small, it may
have some impact in low-power applications.
4.4.2
When BOR is enabled, the BOR bit always resets to ‘0’
on any BOR or POR event. This makes it difficult to
determine if a BOR event has occurred just by reading
the state of BOR alone. A more reliable method is to
simultaneously check the state of both POR and BOR.
This assumes that the POR bit is reset to ‘1’ in software
immediately after any POR event. IF BOR is ‘0’ while
POR is ‘1’, it can be reliably assumed that a BOR event
has occurred.
4.4.3
When BOREN1:BOREN0 = 10, the BOR remains
under hardware control and operates as previously
described. Whenever the device enters Sleep mode,
however, the BOR is automatically disabled. When the
device returns to any other operating mode, BOR is
automatically re-enabled.
This mode allows for applications to recover from
brown-out situations, while actively executing code,
when the device requires BOR protection the most. At
the same time, it saves additional power in Sleep mode
by eliminating the small incremental BOR current.
Note:
BOR Operation
Even when BOR is under software control,
the BOR Reset voltage level is still set by
the BORV1:BORV0 Configuration bits. It
cannot be changed in software.
DETECTING BOR
DISABLING BOR IN SLEEP MODE
© 2006 Microchip Technology Inc.