USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications
Datasheet
6.3
Device Configuration Straps
Configuration straps are multi-function pins that are driven as outputs during normal operation. During
a
or an
these outputs are tri-stated. The high
or low state of the signal is latched following de-assertion of the reset and is used to determine the
default configuration of a particular feature. Configuration straps are latched as a result of a
or a
Configuration strap signals are noted in
and are identified by an underlined symbol name. The following sub-
sections detail the various configuration straps.
Configuration straps include internal resistors in order to prevent the signal from floating when
unconnected. If a particular configuration strap is connected to a load, an external pull-up or pull-down
should be used to augment the internal resistor to ensure that it reaches the required voltage level
prior to latching. The internal resistor can also be overridden by the addition of an external resistor.
Note:
The system designer must guarantee that configuration straps meet the timing requirements
specified in
and
If configuration straps are not
at the correct voltage level prior to being latched, the device may capture incorrect strap
values.
Note:
Configuration straps must never be driven as inputs. If required, configuration straps can be
augmented, or overridden with external resistors.
6.3.1
SPI Speed Select (SPI_SPD_SEL)
This strap is used to select the speed of the SPI as follows:
Table 6.1 SPI_SPD_SEL Configuration Definitions
SPI_SPD_SEL
‘0’
‘1’
DEFINITION
30 MHz SPI Operation (Default)
60 MHz SPI Operation
Note:
If the latched value on reset is 1, this pin is tri-stated when the chip is in the suspend state. If
the latched value on reset is 0, this pin is driven low during a suspend state.
SMSC USB3813
27
Revision 1.0 (06-17-13)
DATASHEET
SMSC [ SMSC CORPORATION ]
