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Datasheet
Revision 1.91 (08-22-07) 18 SMSC USB2524
DATASHEET
Chapter 6 Assigning Ports
There are two different (OEM selectable) methods of assigning downstream ports to upstream hosts.
One method is with the PRT_ASSIGN[3:0] interface through the use of mechanical switches or by
electrical control of the pins via an external Microcontroller’s GPIO interface. The second method is
through the SMBus interface, where the SMBus interface is used to control the switching hub during
operation and can switch downstream ports via SMBus commands.
6.1 Port Assign Interface (PRT_ASSIGN[3:0] pins)
Assigning ports to either of the upstream host controllers can be accomplished through the 4-wire
PRT_ASSIGN interface. The PRT_ASSIGN interface has three operating modes. One is called the
Embedded Mode, and the other is Peripheral Mode (with two different electrical “sub” modes; (level
triggered or edge triggered).
Note: Any change in PRT_ASSIGN pins will be ignored until the USB2524 is out of reset.
6.1.1 Embedded Mode:
The four-pin interface (PRT_ASSIGN[3:0]) operates with only three of the four available pins
(PRT_ASSIGN3 is disabled in this mode), which enables a user to select one of 8 pre-determined port
assignment configurations. There are 8 “default” configurations, or an OEM can customize the
configurations through an EEPROM or SMBus code load.
Note: There is a switching delay determined by the Register D0h: Port Interface Delay Timer.
The configuration is determined by Table 6.1, "USB2524 Port Assign Interface (Embedded Mode)".
Note 6.1 H1 = The USB host or hub that is connected to upstream port #1
Note 6.2 H2 = The USB host or hub that is connected to upstream port #2
Note 6.3 UA = Un-Assigned
Table 6.1 USB2524 Port Assign Interface (Embedded Mode)
PORT ASSIGN INTERFACE ENCODING
INTERNAL DEFAULT
CONFIGURATION
HOST OWNERSHIP OF
DOWNSTREAM PORTS
PRT_ASSIGN
3
PRT_ASSIGN
2
PRT_ASSIGN
1
PRT_ASSIGN
0
CONFIG
#
PORT
1
PORT
2
PORT
3
PORT
4
X 0 0 0 0 H1H1H1H1
X 0 0 1 1 H2H2H2H2
X 0 1 0 2 H1H1H2H2
X 0 1 1 3 H1H1H1H2
X 1 0 0 4 H2H2H2H1
X 1 0 1 5 H2H1H1H1
X1106H1H1H2UA
X1117H1H1H1UA