9 pll clock multiplier, 10 overcurrent detection, 11 i2c-bus interface – Philips Universal Serial Bus ISP1122 User Manual

Page 10: Modes of operation, Table 4 “mode selection, Isp1122, Philips semiconductors, 11 i, C-bus interface

Philips Semiconductors

ISP1122

USB stand-alone hub

Product specification

Rev. 03 — 29 March 2000

10 of 48

9397 750 07002

6.9 PLL clock multiplier

A 6 to 48 MHz clock multiplier Phase-Locked Loop (PLL) is integrated on-chip. This
allows for the use of low-cost 6 MHz crystals. The low crystal frequency also
minimizes Electro-Magnetic Interference (EMI). The PLL requires no external
components.

6.10 Overcurrent detection

An overcurrent detection circuit for downstream ports has been integrated on-chip. It
is self-reporting, resets automatically, has a low trip time and requires no external
components. Both individual and global overcurrent detection are supported.

6.11 I

C-bus interface

A basic serial I

C-bus interface (single master, 100 kHz) is provided to read VID, PID

and configuration bits from an external I

C-bus EEPROM (e.g. Philips PCF8582 or

equivalent). At reset the ISP1122 reads 6 bytes of data from the external memory.

The I

C-bus interface timing complies with the standard mode of operation as

described in

The I

C-bus and how to use it, order number 9398 393 40011.

Modes of operation

The ISP1122 has several modes of operation, each corresponding with a different pin
configuration. Modes are selected by means of pins INDV, OPTION and SP/BP, as
shown in

Table 4

[1]

Port power switching: logic 0 = ganged, logic 1 = individual.

[2]

Power mode: logic 0 = bus-powered, logic 1 = self-powered (or hybrid-powered).

[3]

No overcurrent detection.

[4]

No power switching.

Table 4:

Mode selection

Mode