
ADSP-BF59x Blackfin Processor Hardware Reference
17-9
System Design
Programmable Outputs
During power up, each GPIO pin is set to an input and any pins used in
the system as an output should be connected to a pullup or pulldown
resistor to maintain the desired state.
This would be particularly important in motor drive applications. It is also
important for UART TX and RTS, SPI and serial TWI, or other commu-
nications interfaces. Some memory enable pull-ups may also be desired.
After the boot cycle, each GPIO pin may be set to input or output
depending on ADSP-BF59x model number and the boot cycle chosen.
The I/O / GPIO muxing of all pins may need to be reprogrammed to sup-
port the users application. Care should be taken for compatibility of
function and state, before boot, during boot, and application pin usage.
Voltage Regulation Interface
ADSP-BF59x processors must use an external voltage regulator to power
the V
DDINT
domain. The
EXT_WAKE
and
PG
signals can facilitate commu-
nication with the external voltage regulator.
EXT_WAKE
is high-true for
power-up and low only when the processor is in the hibernate state.
EXT_WAKE
may be connected directly to the low-true shut down input of
many common regulators.
The
PG
(power-good, low-true) signal that allows the processor to start
only after the internal voltage has reached a chosen level. In this way, the
startup time of the external regulator will be detected after hibernation.
If the processor never will enter the hibernate state, the
PG
signal can be
grounded in this mode. This will always indicate 'power good', meaning
that V
DDINT
is at a safe operating level. Any delay required at initial
power-on, to guarantee a safe operating level for V
DDINT
, will be pro-
vided by the
RESET
signal.
Содержание ADSP-BF59x Blackfin
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Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...