USB Port Overview

The USB port has no settings, and is faster than the serial ports, especially for
operations requiring transport of large blocks of data such as long event
reports or firmware upgrades.

Each time you connect a relay to your PC USB port, Windows determines if a
driver has already been installed and is ready for use. There are three
possibilities:

	1. Connect a PC for the first time to a relay USB port.
	Windows launches the Found New Hardware
	Wizard. The wizard guides you through the USB driver
	installation process and creates a new virtual COM port
	(e.g., COM 4).

	2. Reconnect a PC to a relay USB port using a different physical
	USB port on a PC (i.e., same PC, different physical USB port
	on the PC).
		
		Windows launches the Found New Hardware
		Wizard. Select Install the software automatically
		(Recommended) and click Next. Windows locates the
		required INF file and driver, and creates a new virtual
		COM port (e.g., COM 5).
		
		Windows creates a new virtual COM port (e.g., COM 6,
		COM 7) each time you connect a relay to a physical
		USB port that has not previously been connected to a
		relay. The virtual COM port number remains associated
		with the same physical USB port until you uninstall the
		driver.

	3. Reconnect a PC to a relay USB port using a physical USB port
	on the PC that has already been connected to a relay (i.e., same
	PC, same physical USB port on the PC).
		
		Windows recognizes that the driver is already installed,
		and creates the same virtual COM port created the first
		time you connected a relay to that particular physical
		USB port (e.g., COM 4). No action is required on your
		part.

The USB driver exposes normal communications port settings to the personal
computer operating system, such as baud rate, parity, etc. to maintain
compatibility with many PC applications. Changing these settings in the PC
does not change how the relay USB port operates. You may use a PC Terminal
Emulator program or dedicated software to connect to the SEL-351 via USB
port.

USB uses a connection based protocol. Under certain circumstances, such as
power cycling the relay, the USB connection may be terminated. If the USB
connection is terminated it may be necessary to reconnect to the relay using
the PC application software, or disconnect and then reconnect the USB
connector at either the PC or the relay.

ACSELERATOR QuickSet is more tolerant to unexpected USB device
disconnections than most other PC applications. While using ACSELERATOR
QuickSet, it is possible to disconnect the USB cable from one relay and move
it to another relay without the need to restart the application, reselect the COM
port, or even disconnect and reconnect at the application level.