CC2480_11 Datasheet, PDF (23/48 Pages) Texas Instruments – Z-Accel 2.4 GHz ZigBee Processor

CC2480
9 Peripherals
In the following sub-sections the user-
accessible CC2480 peripheral modules are
described
in
detail.
9.1 Reset
The CC2480 has four reset sources. The
following events generate a reset:
• Forcing RESET_N input pin low
• A power-on reset condition
• A brown-out reset condition
•A
firmware-generated
(SYS_RESET_REQ [2])
reset
The initial conditions after a reset are as
follows:
• I/O pins are configured as inputs with pull-
up
• See the CC2480 Interface Specification [2]
for a description of the interaction between
CC2480 and the host processor after
reset.
9.1.1 Power On Reset and Brown Out Detector
The CC2480 includes a Power On Reset (POR)
providing correct initialization during device
power-on. Also includes is a Brown Out
Detector (BOD) operating on the regulated
1.8V digital power supply only, The BOD will
protect the memory contents during supply
voltage variations which cause the regulated
1.8V power to drop below the minimum level
required by flash memory and SRAM.
When power is initially applied to the CC2480
the Power On Reset (POR) and Brown Out
Detector (BOD) will hold the device in reset
state until the supply voltage reaches above
the Power On Reset and Brown Out voltages.
Figure 6 shows the POR/BOD operation with
the 1.8V (typical) regulated supply voltage
together with the active low reset signals
BOD_RESET and POR_RESET shown in the
bottom of the figure (note that signals are not
available, just for illustration of events).
VOLT
1.8V REGULATED
UNREGULATED
BOD RESET ASSERT
POR RESET DEASSERT RISING VDD
POR RESET ASSERT FALLING VDD
0
POR OUTPUT _X
X
BOD RESET
X
X
POR RESET _X
X
Figure 6 : Power On Reset and Brown Out Detector Operation
9.2 I/O ports
The CC2480 has digital input/output pins that
have the following key features:
• General purpose I/O or peripheral I/O
• Pull-up or pull-down capability on inputs
• External interrupt capability
Two of the I/O pins have external interrupts
that can be used to wake up the device from
sleep modes.
CC2480 Data Sheet SWRS074
Page 23 of 43