SMSC USB2502 - Manual (Page 13)

2-Port USB 2.0 Hub Controller
Datasheet
SMSC USB2502 13 Revision 2.3 (08-27-07)
DATASHEET
SERIAL PORT INTERFACE
Serial Data/SMB
Data
SDA/SMBDATA IOSD12 (Serial Data)/(SMB Data) signal.
Serial Clock/SMB
Clock
&
Config Select 0
SCL/SMBCLK/
CFG_SEL0
IOSD12 (Serial Clock)/(SMB Clock) signal. This multifunction pin is
read on the rising edge of RESET_N (see the applicable
RESET_N timing table in
Section 5.6.1 ) and will determine
the hub configuration method as described in Table 4.2 .
Configuration
Programming
Select
CFG_SEL1 I This pin is read on the rising edge of RESET_N (see the
applicable RESET_N timing table in
Section 5.6.1 ) and will
determine the hub configuration method as described in
Table 4.2 .
Table 4.2 SMBus or EEPROM Interface Behavior
CFG_SEL1 CFG_SEL0 SMBus or EEPROM interface behavior.
0 0 Reserved
0 1 Configured as an SMBus slave for external download of user-
defined descriptors. SMBus slave address is 0101100
1 0 Internal Default Configuration via strapping options.
1 1 2-wire (I2C) EEPROMS are supported,
Table 4.3 Miscellaneous Pins
NAME SYMBOL TYPE FUNCTION
Crystal
Input/External
Clock Input
XTAL1/
CLKIN
ICLKx 24MHz crystal or external clock input.
This pin connects to either one terminal of the crystal or
to an external 24MHz clock when a crystal is not used.
Crystal Output XTAL2 OCLKx 24MHz Crystal
This is the other terminal of the crystal, or left
unconnected when an external clock source is used to
drive XTAL1/CLKIN. It must not be used to drive any
external circuitry other than the crystal circuit.
Clock Input
Enable
CLKIN_EN I Clock In Enable:
Low = XTAL1 and XTAL2 pins configured for use with
external crystal
High = XTAL1 pin configured as CLKIN, and must be
driven by an external CMOS clock.
RESET Input RESET_N IS This active low signal is used by the system to reset the
chip. The minimum active low pulse is 1us.
Self-Power /
Bus-Power
Detect
SELF_PWR I Detects availability of local self-power source.
Low = Self/local power source is NOT available (i.e., Hub
gets all power from Upstream USB VBus).
High = Self/local power source is available.
TEST Pin TEST IPD Used for testing the chip. User must treat as a no-
connect or connect to ground.
Table 4.1 2-Port Hub Pin Descriptions (continued)
NAME SYMBOL TYPE FUNCTION