25
RS232 Character Set
Because of the need for XON/XOFF handshake it is possible to send ASCII coded data only;
binary blocks are not allowed. Bit 7 of ASCII codes is ignored, i.e. assumed to be low. No
distinction is made between upper and lower case characters in command mnemonics and they
may be freely mixed. The ASCII codes below 20H (space) are not used. In this manual 20H, etc.
means 20 in hexadecimal.
USB Interface
(QPX600DP only)
The USB interface allows the instrument to be controlled using RS232 protocol via a computer’s
USB port. The instrument is supplied with a CD containing an .inf file for the standard Microsoft
drivers available in Windows 2000, XP, Vista and Windows 7; the installation wizard will install the
driver (32-bit or 64-bit) appropriate to the PC’s operating system. Any updates are available via
the TTi website, www.tti-test.com.
Installation of the interface driver is achieved by connecting the instrument to a PC via a standard
USB cable. The Windows’ plug and play functions should automatically recognise the addition of
new hardware attached to the USB interface and, if this is the first time the connection has been
made, prompt for the location of a suitable driver. Provided that the standard Windows prompts are
followed correctly Windows will install the appropriate driver and establish a virtual COM port within
the PC. The number of the new COM port will depend upon the number of co-existing COM ports
within the PC. The virtual COM port can be driven by Windows applications in exactly the same
way as a standard COM port, except that the Baud rate setting of the virtual COM port is ignored.
The driver will remain installed on the PC so that the establishment of a virtual COM port is done
automatically each time the instrument is connected to the PC via USB in the future.
Further virtual COM ports are created for each additional instrument connected to the PC via USB.
Each instrument is assigned a separate virtual COM port when it is first connected and the same
COM port will be assigned each time that instrument is subsequently connected; the PC software
makes use of the unique code embedded in each instrument to link it to the same virtual COM port
irrespective of which physical USB port it is connected to.
LAN Interface
(QPX600DP only)
The LAN interface is designed to comply with the LXI standard version 1.2 Class C and contains
the interfaces and protocols described below. Since it is possible to misconfigure the LAN
interface, making it impossible to communicate with the instrument over LAN, a LAN Configuration
Initialise (LCI) mechanism is provided via a recessed switch on the rear panel to reset the unit to
the factory default. The default setting is for the instrument to attempt to obtain settings via DHCP
if available or, if DHCP times out (30 seconds), via Auto-IP. In the very unlikely event that an Auto-
IP address cannot be found a static IP address of 192.168.0.100 is assigned. Resetting the LAN
removes any password protection.
For more information on LXI standards refer to www.lxistandard.org/home .
LAN Connection
To use the LAN interface, the IP address of the unit must be known. There is a LXI Discovery Tool
on the supplied CD-ROM which can be used to display the IP addresses (and other associated
information) of all connected devices that comply with the VXI-11 discovery protocol. This tool is a
Windows PC application that should be installed and run on the controlling PC with the unit either
connected directly to the PC network connector or via a router. Connecting via a router is
recommended as this is significantly quicker to assign an IP address; connecting directly to the PC
will begin to assign an IP address only after a 30 second DHCP timeout.
Double clicking on any entry in the list of devices discovered will open the PC's web browser and
display the Home page of that device.
There are also tools for LAN discovery included as part of the National Instruments Measurement
and Automation Explorer package and the Agilent Vee application.
The unit will, when first powered up, attempt to obtain settings via DHCP if available or, if DHCP
times out (30 seconds), via Auto-IP. In the very unlikely event that an Auto-IP address cannot be
found a static IP address of 192.168.0.100 is assigned.
