Stand-Alone Hub Specification Sheet

Philips Semiconductors
ISP1122
USB stand-alone hub
Product specification Rev. 03 — 29 March 2000 20 of 48
9397 750 07002
© Philips Electronics N.V. 2000. All rights reserved.
9.4.6 Get configuration descriptor
The hub returns 25 bytes containing the configuration descriptor (9 bytes, see
Tabl e 11), the interface descriptor (9 bytes, see Table 1 2) and the endpoint descriptor
(7 bytes, see Table 1 3).
9.4.7 Get device descriptor
The hub returns 18 bytes containing the device descriptor, see Table 1 0.
9.4.8 Get hub descriptor
The hub returns 9 bytes containing the hub descriptor, see Table 1 4.
9.4.9 Get string descriptor (0)
The hub returns 4 bytes containing the language ID, see Table 1 5.
9.4.10 Get string descriptor (1)
The hub returns 46 bytes containing the manufacturer name, see Tabl e 1 5.
9.4.11 Get string descriptor (2)
The hub returns 16 bytes containing the product name, see Tabl e 15.
10. I
2
C-bus interface
A simple I
2
C-bus interface is provided in the ISP1122 to read customized vendor ID,
product ID and some other configuration bits from an external EEPROM. The
interface supports single master operation at a nominal bus speed of 93.75 kHz.
The I
2
C-bus interface is intended for bidirectional communication between ICs via two
serial bus wires, SDA (data) and SCL (clock). Both lines are driven by open-drain
circuits and must be connected to the positive supply voltage via pull-up resistors.
10.1 Protocol
The I
2
C-bus protocol defines the following conditions:
•
Bus free: both SDA and SCL are HIGH
•
START: a HIGH-to-LOW transition on SDA, while SCL is HIGH
•
STOP: a LOW-to-HIGH transition on SDA, while SCL is HIGH
•
Data valid: after a START condition, data on SDA are stable during the HIGH
period of SCL; data on SDA may only change while SCL is LOW.
Each device on the I
2
C-bus has a unique slave address, which the master uses to
select a device for access.
The master starts a data transfer using a START condition and ends it by generating
a STOP condition. Transfers can only be initiated when the bus is free. The receiver
must acknowledge each byte by means of a LOW level on SDA during the ninth clock
pulse on SCL.
For detailed information please consult The I
2
C-bus and how to use it ., order number
9398 393 40011.