USB2533 datasheet(29/61 Pages) SMSC

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USB 2.0 Hi-Speed 3-Port Hub Controller

Datasheet

SMSC USB2533

Revision 1.0 (06-17-13)

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 57 and Section

9.5.1, "Power-On Configuration Strap Valid Timing," on page 56. 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 [3:1]

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:

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

Configuration Select (CFG_SEL[1:0])

Refer to Section 6.1, "Configuration Method Selection," on page 26 for details on CFG_SEL[1:0].

6.3.3

Downstream Battery Charging Enable (BC_EN[3:1])

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

Table 6.2 NON_REM[1:0] Configuration Definitions

NON_REM[1:0]

DEFINITION

‘00’

All USB ports removable, SUSP_IND LED active high

‘01’

Port 1 is non-removable, SUSP_IND LED active low

‘10’

Ports 1 & 2 are non-removable, SUSP_IND LED active high

‘11’

Ports 1, 2 & 3 are non-removable, SUSP_IND LED active low

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