Datasheet

USB 2.0 Hi-Speed Hub Controller
Datasheet
Revision 1.1 (04-26-10) 56 SMSC USB251x
DATASHEET
Figure 8.3 Non-Removable Pin Strap Example
8.6.2 Internal Pull-Down (IPD)
If a pin's strap function is enabled thru hub configuration selection, (Table 8.1 Hub Configuration
Selection) and the strap pins driver type is IPD/O (internal pull-down for the Input function), use this
type of strap option.
The following figure shows an example of Strap High and Strap Low. Use the Strap High configuration
to set the strap option value to a ‘1’. Use the Strap Low configuration to set the strap option value to 0.
Figure 8.4 Pin Strap Option with IPD Pin Example
8.6.3 LED Strap Option
If a pin’s strap function of the LED pins are enabled thru the internal default configuration, the driver
type of each strap pin is I/O (no internal pull-up or pull-down for the input function). When the strap
pin shares functionality with an LED, use this type of strap option.
The internal logic will drive the LED appropriately (active high or low) depending on the sampled strap
option. Figure 8.5 shows an example of Strap High and Strap Low. Use the Strap High configuration
to set the strap option value to a ‘1’. Use the Strap Low configuration to set the strap option value to ‘0’.
Figure 8.5 LED Pin Strap Example
HUB
Strap Pin
Primary Function/
Strap High
+V
HUB
Strap Pin
Primary Function/
Strap Low
GND
R kΩ
R kΩ
HUB
Strap Pin (IPD)
Primary Function/
Strap High
R kΩ
+V
VSS
HUB
Strap Pin (IPD)
Primary Function/
Strap Low
VSS
HUB
Strap Pin
LED/
Strap High
HUB
Strap Pin
LED/
Strap Low
R
kΩ
R
kΩ