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Philips Semiconductors
ISP1122
USB stand-alone hub
Product specification Rev. 03 — 29 March 2000 10 of 48
9397 750 07002
© Philips Electronics N.V. 2000. All rights reserved.
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
2
C-bus interface
A basic serial I
2
C-bus interface (single master, 100 kHz) is provided to read VID, PID
and configuration bits from an external I
2
C-bus EEPROM (e.g. Philips PCF8582 or
equivalent). At reset the ISP1122 reads 6 bytes of data from the external memory.
The I
2
C-bus interface timing complies with the standard mode of operation as
described in
The I
2
C-bus and how to use it
, order number 9398 393 40011.
7. 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 Tabl e 4.
[1] Port power switching: logic 0 = ganged, logic 1 = individual.
[2] Power mode: logic0=bus-powered, logic 1 = self-powered (or hybrid-powered).
[3] No overcurrent detection.
[4] No power switching.
Table 4: Mode selection
Mode INDV
[1]
OPTION SP/BP
[2]
PSWn/GLn
(n = 1 to 4)
PSW5/GL5/GPSW OCn
(n = 1 to 4)
OC5/GOC
0000GoodLink ganged power inactive global overcurrent
1001GoodLink ganged power inactive global overcurrent
2010GoodLink ganged power inactive
[3]
inactive
[3]
3011GoodLink
[4]
GoodLink
[4]
inactive global overcurrent
4100individual power inactive individual
overcurrent
inactive
5101individual power individual power individual
overcurrent
individual
overcurrent
6110individual power inactive inactive
[3]
inactive
[3]
7111GoodLink
[4]
GoodLink
[4]
individual
overcurrent
individual
overcurrent