ISP1521 datasheet(18/53 Pages) PHILIPS

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Philips Semiconductors

ISP1521

Hi-Speed USB hub controller

Product data

Rev. 03 — 24 November 2004

18 of 53

9397 750 13702

9.2.2

Architecture of conﬁgurable hub descriptors

The conﬁgurable hub descriptors can be masked in the internal ROM memory; see

Figure 7. These descriptors can also be supplied from an external EEPROM or a

microcontroller. The ISP1521 implements both the master and slave I2C-bus

controllers. The information from the external EEPROM or the microcontroller is

transferred into the internal RAM during the power-on reset. A signature word is used

to identify correct descriptors. If the signature matches, the content of the RAM is

chosen instead of the ROM.

When the external microcontroller mode is selected and while the external

microcontroller is writing to the internal RAM, any request to conﬁgurable descriptors

will be responded to with a Not AcKnowledge (NAK). There is no speciﬁed time-out

period for the NAK signal. This data is then passed to the host during the

enumeration process.

The three conﬁguration methods are selected by connecting pins SCL and SDA in the

manner given in Table 11.

The I2C-bus cannot be shared between the EEPROM and the external microcontroller.

Fig 7.

Conﬁgurable hub descriptors.

Table 11:

Conﬁguration method

SCL

SDA

Internal ROM

ground

External EEPROM

2.2 k

Ω to 4.7 kΩ pull-up

2.2 k

Ω to 4.7 kΩ pull-up

External microcontroller

driven LOW by the

microcontroller during reset

2.2 k

Ω to 4.7 kΩ pull-up

MLD711

MICROCONTROLLER

SERIAL EEPROM

MASTER/SLAVE

I2C-BUS INTERFACE

signature

match

RAM

(256 bytes)

DESCRIPTOR

GENERATOR

INTERFACE

ROM

(256 bytes)

MUX

HUB CORE

I2C-bus

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