Datasheet

USB 2.0 Hi-Speed Hub Controller
Datasheet
Revision 2.3 (06-11-13) 18 SMSC USB251xB/xBi
DATASHEET
SERIAL PORT INTERFACES
SDA/ I/OSD12 Serial Data Signal
SMBDATA/ System Management Bus Signal
NON_REM1 Non-Removable Port 1 Strap Option: when enabled by package and
configuration options (see Table 5.1 on page 24), this pin will be sampled (in
conjunction with LOCAL_PWR/SUSP_IND/NON_REM0) at RESET_N negation
to determine if ports [x:1] contain permanently attached (non-removable)
devices:
NON_REM[1:0] = 00 : all ports are removable
NON_REM[1:0] = 01 : port 1 is non-removable
NON_REM[1:0] = 10 : ports 1 and 2 are non-removable
NON_REM[1:0] = 11 : when available, ports 1, 2, and 3 are non-removable
When NON_REM[1:0] is chosen such that there is a non-removable device, the
hub will automatically report itself as a compound device (using the proper
descriptors).
RESET_N IS RESET Input: the system can reset the chip by driving this input low. The
minimum active low pulse is 1 μs.
SCL/ I/OSD12 Serial Clock (SCL)
SMBCLK/ System Management Bus Clock
CFG_SEL0 Configuration Select: the logic state of this multifunction pin is internally latched
on the rising edge of RESET_N (RESET_N negation), and will determine the hub
configuration method as described in Tab l e 5. 1.
HS_IND/ I/O12 Hi-Speed Upstream Port Indicator: upstream port connection speed.
Asserted = the hub is connected at HS
Negated = the hub is connected at FS
Note: When implementing an external LED on this pin, the active state is
indicated above and outlined in Section 3.3.1.3, on page 21.
CFG_SEL1 Configuration Programming Select 1: the logic state of this pin is internally
latched on the rising edge of RESET_N (RESET_N negation), and will determine
the hub configuration method as described in Ta bl e 5.1 .
MISC
XTALIN ICLKx Crystal Input: 24 MHz crystal.
This pin connects to either one terminal of the crystal or to an external 24 MHz
clock when a crystal is not used.
CLKIN External Clock Input: this pin connects to either one terminal of the crystal or to
an external 24 MHz clock when a crystal is not used.
XTALOUT OCLKx Crystal Output: this is the other terminal of the crystal circuit with 1.2 V p-p output
and a weak (< 1mA) driving strength. When an external clock source is used to
drive XTALIN/CLKIN, leave this pin unconnected, or use with appropriate
caution.
Table 3.2 USB251xB/xBi Pin Descriptions (continued)
SYMBOL
BUFFER
TYPE DESCRIPTION