USB2524-ABZJ Standard Microsystems (SMSC), USB2524-ABZJ Datasheet - Page 19

• Manufacturer Part Number: USB2524-ABZJ
• Manufacturer: Standard Microsystems (SMSC)

Specifications of USB2524-ABZJ

• Lead Free Status / RoHS Status: Compliant

USB MultiSwitch
Datasheet
SMSC USB2524
6.1.2
6.1.3
6.2
Note 6.4
Peripheral Mode: Level Triggered
In Peripheral Mode (Level Triggered), each pin directly switches a downstream port between the two
upstream host ports. Each pin on the PRT_ASSIGN interface is only capable of two electrical states
(either logic low or logic high). The interface will control downstream port assignment as follows.
Note: There is a switching delay determined by the Register D0h: Port Interface Delay Timer.
PRT_ASSIGN0 = '0', then Port 1 assigned to host 1
PRT_ASSIGN0 = '1', then Port 1 assigned to host 2
PRT_ASSIGN1 = '0', then Port 2 assigned to host 1
PRT_ASSIGN1 = '1', then Port 2 assigned to host 2
PRT_ASSIGN2 = '0', then Port 3 assigned to host 1
PRT_ASSIGN2 = '1', then Port 3 assigned to host 2
PRT_ASSIGN3 = '0', then Port 4 assigned to host 1
PRT_ASSIGN3 = '1', then Port 4 assigned to host 2
Peripheral Mode: Edge Triggered
Each pin will respond to a positive edge transition that is part of a positive pulse that has a minimum
pulse width of 100ns, and will not respond to another positive edge until after a negative pulse with
minimum pulse width (that is determined by the
0x00) on page
programmable length negative width requirement provides an effective glitch filter mechanism for a
variety of mechanical switches.
Each positive edge transition will change the upstream host ownership of downstream ports as follows
(1st transition will increment ownership from Host 1 to Host 2, the 2nd transition will increment
ownership from Host 2 to Unassigned (or Host 1, if not using the Unassigned state), and the 3rd
transition will increment ownership from Unassigned to Host 1 (note: this “3rd” state will not occur if
“unassigned” is not used). Each subsequent transition will continue to increment the port ownership
and will cycle through in similar fashion.
Note: Power-On default for edge triggered operation is: all ports assigned to Host 1.
In this mode, the SMBus interface remains “live” during operation of the switching hub and is used to
switch/assign ports “on-the-fly” through SMBus commands. This is accomplished through register
direct writes to the Port Assignment registers (see the USB_ATTACH description under
Status/Command (Reset = 0x00) on page
SMBus Host Control of Port Assignment
TM
Hub
X = Don’t Care
29) has been detected. The combination of a 100ns positive pulse width and a
DATASHEET
19
39).
Register D0h: Port Interface Delay Timer (Reset =
Revision 1.91 (08-22-07)
Register FFh: