PIC16F818/819
12.0
SPECIAL FEATURES OF
THE CPU
Sleep mode is designed to offer a very low-current
power-down mode. The user can wake-up from Sleep
through external Reset, Watchdog Timer wake-up or
through an interrupt.
Several oscillator options are also made available to
allow the part to fit the application. The RC oscillator
option saves system cost while the LP crystal option
saves power. Configuration bits are used to select the
desired oscillator mode.
Additional information on special features is available
in the
“PICmicro
®
Mid-Range MCU Family Reference
Manual”
(DS33023).
These devices have a host of features intended to
maximize system reliability, minimize cost through elimi-
nation of external components, provide power-saving
operating modes and offer code protection:
• Reset
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• Sleep
• Code Protection
• ID Locations
• In-Circuit Serial Programming
There are two timers that offer necessary delays on
power-up. One is the Oscillator Start-up Timer (OST),
intended to keep the chip in Reset until the crystal oscil-
lator is stable. The other is the Power-up Timer (PWRT)
which provides a fixed delay of 72 ms (nominal) on
power-up only. It is designed to keep the part in Reset
while the power supply stabilizes and is enabled or
disabled using a configuration bit. With these two
timers on-chip, most applications need no external
Reset circuitry.
12.1
Configuration Bits
The configuration bits can be programmed (read as
‘0’), or left unprogrammed (read as ‘1’), to select
various device configurations. These bits are mapped
in program memory location 2007h.
The user will note that address 2007h is beyond the
user program memory space which can be accessed
only during programming.
2004 Microchip Technology Inc.
DS39598E-page 89
MICROCHIP [ MICROCHIP TECHNOLOGY ]
