Data Sheet
IEEE-1394 PC Link to VXI, C-Size
Agilent E8491B
•
C-size, 1-slot, message-based commander
•
Industry standard PC-to-VXI interface
•
High-performance data block transfers
•
Ease of configuration with hot plug-in capability
•
Supports multiple mainframes with one PC
•
Timing and triggering to external devices/mainframes
Description
The Agilent Technologies E8491B IEEE-1394 PC Link to VXI
is a C-size, 1-slot, message-based VXI module, providing a
direct connection from your PC to a VXI mainframe via the
industry standard IEEE-1394 bus (FireWire).
The E8491B is a high-speed C-size device with Resource
Manager and Slot 0 capability. Its logical address is 0,
therefore it is always the mainframe’s Resource Manager
and is typically installed in mainframe Slot 0. The high
speed is accomplished, in part, through the use of small
signals (200 mV) that are transmitted differentially over the
twisted-pair wire set with controlled-impedance
characteristics. The differential signal provides high-noise
immunity.
The E8491B includes a C-size VXI Slot 0 module and a 4.5meter cable. Ease of configuration is achieved with
automatic recognition of a new IEEE-1394-based device
without powering down the PC, known as “hot plug-in”.
The E8491B Option 001 is an OHCI-based IEEE-1394/PCI
host adapter card. It is a PC plug-in card capable of
transferring data at up to 400 Mbits/second. The card has
three external 1394 ports. If required, the OHCI-based
IEEE-1394/PCI card can supply 12V at up to 1.5A for
IEEE-1394 devices that require power.
Refer to the Agilent Technologies Website
(www.agilent.com/find/vxi)
for recent product updates, if
applicable.
Agilent E8491B
2
IEEE-1394 Applications
The E8491B is well suited for data acquisition applications
moving large blocks of data, and it is a cost-effective choice
for test applications when used with Agilent’s E84XX
mainframe series. For multiple VXI mainframe systems,
one E8491B is installed into each mainframe and these are
interconnected via the cable in a daisy-chain, tree or star
configuration. Up to 16 mainframes can be supported from
one PC. This reduces the system cost further since an
additional OHCI-based IEEE-1394/PCI card is not needed
for each added mainframe.
The E8491B includes clock and triggering capabilities, plus
complete SICL/VISA I/O library software for the Windows
®
95/98/Me/NT®4.0/2000 environments. The interface also
supports 32-bit Interpreted SCPI (I-SCPI).
What is IEEE-1394?
“FireWire”, “IEEE-1394”, “IEC 1883”…. These titles refer to
a high-speed serial bus that is literally a new standard for
transmitting data between PCs and consumer electronics.
“FireWire”, as named by its inventors at Apple Computer
Inc., was born out of the need for a low-cost, consumer
oriented connection for applications where large amounts
of digital audio and video data is recorded, edited, stored,
and transferred between devices. The bus’ performance,
flexibility, and ease-of-use resulted in an implementation
as an I/O interconnect (Agilent E8491B) between external
PCs and C-size VXI mainframes.
IEEE-1394’s reduction in cost is, in part, achieved through
serial data transfer, which uses a simplified cable design.
The IEEE-1394 cable medium allows up to 16 physical
connections (cable hops) on one bus segment, each up to
4.5 meters in length. (The cable supplied with the E8491B
is 4.5 meters.) This gives a system using IEEE-1394 a total
cable distance of 72 meters. The data is transmitted over
one of the cables’ twisted-pair sets, while the other twistedpair set is used for the clock. The clock makes a transition
when the data line does not, allowing a simple,
exclusive-OR gate to be used for clock recovery.
IEEE-1394’s reduction in cost and ease of use are also
attained through simplified electronics. Its transmitters
and receivers, which are available as a standard chip set,
handle addressing, initialization, arbitration and protocol.
The plug-and-play nature of the IEEE-1394 bus is also
achieved in this chip set. Node addresses, for example, are
assigned to devices on the bus upon power-up.
Data transfer over the IEEE-1394 bus can be either
Asynchronous or Isochronous. Both types can occur on the
same bus. Isochronous data transfers broadcast variable
amounts of data to multiple “channels” at a regular
intervals with no acknowledgment. Asynchronous data
transfers use a “fair arbitration” protocol to ensure each
IEEE-1394 device has equal access to the bus. The E8491B
supports asynchronous data transfers to secure equal
access for each VXI mainframe.
Product Specifications
Interface Characteristics
Operating system: Windows 95/98/Me/NT 4.0/2000
Controllers: PC based
I/O Library: SICL/VISA
PC backplane: PCI 2.1 with latest BIOS
Max. sustained data transfer:
16 bit: 14 MB/sec
32 bit: 14 MB/sec
Max. backplane burst rate:
16 bit: 13 MB/sec
32 bit: 27 MB/sec
64 bit: 53 MB/sec
Languages: C/C++, Visual Basic, Agilent VEE,
LabVIEW/VISA,
LabWindows/VISA
General Characteristics
Interface: IEEE-1394
Slot 0 functions: Yes
Resource manager: Yes
Extended VXIbus resource manager: Yes
CLK10: Yes
D16 Read
Kbytes/s
D16 Write
Kbytes/s
D32 Read
Kbytes/s
D32 Write
Kbytes/s
Agilent
E8491B
FireWire 8600 10200 12000 14000
Agilent
E1406A
GPIB
700 700
N/A
(Not
supported)
N/A
(Not
supported)
Agilent
E6235A
200 MHz
Embedded
VXI PC
8500 1600 14000 3100
Large Block (>64 Kbytes) Data Transfer Rate
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