USB 2.0 Hi-Speed 2-Port Hub Controller
Datasheet
6.3
Device Configuration Straps
Configuration straps are multi-function pins that are driven as outputs during normal operation. During
a Power-On Reset (POR) or an External Chip Reset (RESET_N), 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 Power-On
Reset (POR) or a External Chip Reset (RESET_N). Configuration strap signals are noted in Chapter 3,
"Pin Descriptions," on page 10 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 Section 9.5.2, "Reset and Configuration Strap Timing," on page 56 and Section
9.5.1, "Power-On Configuration Strap Valid Timing," on page 55. 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
Non-Removable Device (NON_REM[1:0])
The NON_REM[1:0] configuration straps are sampled at RESET_N negation to determine if ports [2:1]
contain permanently attached (non-removable) devices as follows. Additionally, because the
SUSP_IND indicator functionality is shared with the NON_REM0 configuration strap, the active state
of the LED connected to SUSP_IND will be determined as follows:
Table 6.2 NON_REM[1:0] Configuration Definitions
NON_REM[1:0]
DEFINITION
‘00’
‘01’
‘10’
‘11’
All USB ports removable, SUSP_IND LED active high
Port 1 is non-removable, SUSP_IND LED active low
Ports 1 & 2 are non-removable, SUSP_IND LED active high
Ports 1 & 2 are non-removable, SUSP_IND LED active low
Note: If using the local power detect function (LOCAL_PWR pin), the NON_REM[1:0] configuration
straps cannot be used to configure the non-removable state of the USB ports. In this case, the
non-removable state of the ports must be configured in internal device registers via the
Protouch tool or SMBus.
6.3.2
6.3.3
Configuration Select (CFG_SEL[1:0])
Refer to Section 6.1, "Configuration Method Selection," on page 25 for details on CFG_SEL[1:0].
Downstream Battery Charging Enable (BC_EN[2:1])
The battery charging enable configuration straps are used to enable battery charging on the
corresponding downstream port. For example, if BC_EN1 is driven high during the configuration strap
Revision 1.0 (06-17-13)
28
SMSC USB2532
DATASHEET
SMSC [ SMSC CORPORATION ]
