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ISP1130

Universal Serial Bus compound hub with integrated keyboard controller

Philips Electronics 

Philips Semiconductors

ISP1130

USB compound hub with keyboard controller

6.7 GoodLink

Indication of a good USB connection is provided through GoodLink technology. An

LED can be directly connected via an external 330 Ω resistor. The ISP1130 supports

GoodLink indication for the hub (upstream port) via output MEMSEL/UPGL and for

the two downstream ports via OCn/DPGLn, controlled via bits GL-MEMSELSelection

and EnableOverCurrent in the USBCON register (see Table 53).

During enumeration the LED blinks on momentarily. After successful configuration of

the ISP1130, the LED is permanently on. The hub GoodLink indicator blinks off for

approximately 128 ms when the hub receives a packet addressed to it. Downstream

GoodLink indicators blink upon an acknowledgment from the associated port. In

‘suspend’ mode the LED is off.

This feature provides a user-friendly indication of the status of the hub, the connected

downstream devices and the USB traffic. It is a useful diagnostics tool to isolate faulty

USB equipment and helps to reduce field support and hotline costs.

6.8 SoftConnect

The connection to the USB is accomplished by bringing D+ (for full-speed USB

devices) HIGH through a 1.5 kΩ pull-up resistor. In the ISP1130, the 1.5 kΩ pull-up

resistor is integrated on-chip and by default is disconnected from the +3.3 V supply.

The integrated microcontroller controls the connection of the internal resistor on D+ to

Vpu(3.3) via bit SoftConnect_N in the USBCON register (see Table 53). Bit Connect in

the Device Status register switches on Vpu(3.3) (default is off) to an alternative external

pull-up resistor. A functional schematic diagram is given in Figure 4.

9397 750 06895

Objective specification

idth

ISP1130

Vpu(3.3)

Connect

(Device Status

Register)

3.3 V

supply

SoftConnect_N

(Configuration

Register)

Fig 4. SoftConnect control logic.

1.5 kΩ

(internal

pull-up)

1.5 kΩ

(external

pull-up)

MGL920

UP_DP

This mechanism allows the microcontroller to complete its initialization sequence

before deciding to establish connection to the USB. Re-initialization of the USB

connection can also be performed without disconnecting the cable.

It should be noted that the tolerance of the internal resistors is higher (30%) than is

specified by the USB specification (5%). However, the overall VSE voltage

specification for the connection can still be met with good margin (see Table 92). The

decision to use this feature lies with the USB equipment designer.

Rev. 01 — 23 March 2000

© Philips Electronics N.V. 2000. All rights reserved.

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