ata5780 ATMEL Corporation, ata5780 Datasheet - Page 19

• Manufacturer Part Number: ata5780
• Description: Uhf Ask/fsk Receiver
• Manufacturer: ATMEL Corporation

4.5.2.2
4.5.3
4.5.4
9207BS–RKE–01/11
Resets
Reset Sources
VS_PA Supply Regulator
This regulator provides the supply voltage for the power amplifier in the RF front end. It has to
be enabled every time a transmit operation is performed.
During reset, all I/O registers are set to their initial values and the program starts execution
from the reset vector. The instruction placed at the reset vector must be a JMP - Absolute
Jump - instruction to the reset handling routine. If the program never enables an interrupt
source, the interrupt vectors are not used and regular program code can be placed at these
locations. This is also the case if the reset vector is in the application section while the inter-
rupt vectors are in the boot section or vice-versa. The circuit diagram in
shows the reset logic.
The I/O ports of the AVR
becomes active. This does not require a clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the internal
reset. This allows the power to reach a stable level before normal operation starts. The
time-out period of the delay counter is defined by the hardware.
There are three sources for reset:
The RF front end has a separate reset circuit for monitoring AVCC voltage.
• Brown-out (DVCC) reset. The MCU is reset when the supply voltage DVCC is below the
• External reset. The MCU is reset when a low level is present on the NRESET pin at the
• Watchdog reset. The MCU is reset when the watchdog is enabled and the watchdog timer
brown-out reset threshold (VBOT). The brown-out detector is always enabled.
external NRESET input for longer than the minimum pulse length.
period expires.
®
are immediately reset to their initial state when a reset source
Atmel ATA5780 [Preliminary]
Figure 4-4 on page 20
19