Operating instructions

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Documentation FireView – Distributed by Allied Vision Technologies
4.6 Bandwidths and limits
As a rule of thumb you can transmit with 400 Mb/s up to 1000q (4000 Bytes) isochronous
data per cycle.
In the example above this means that the bus is 32% loaded with this one camera in this
setting.
Vice versa it means that from the IEEE1394 bandwidth standpoint we should be able to con-
nect up to three cameras with this node (which is true for now-a-days PC’s).
With the color pendant DFW-SX900 (Format_2 Mode_0) we have a load of 64%.
We cannot run two cameras with the max. settings on one node.
But we can if we lower the framerate to 3,75 Hz, because this halves the bus load.
Things are different when we consider the multiplex mode:
Assuming one shot software or hardware trigger, we could connect three cameras per node.
We then trigger the cameras sequentially, just taking care that data transmission does not
overlap.
4.7 Multiple IEEE1394 adapter cards in one PC
FIRESTACK OHCI and FireView is able to handle multiple cards and cameras.
Up to four (three: PCILynx) cameras can be handled per card. Restrictions may apply de-
pending on settings.
When you use multiple cards and cameras be aware that you will reach the bandwidth limit
of the PCI- Bus fairly quickly.
Do not calculate with 132 Mbyte/s (33 MHz x 32 Bit), because this is only a theoretical limit
for the burst mode.
In practise various PC’s showed limits above app. 6000 Byte/cycle data transfer.
FIFO overflows occur and the images start getting corrupted.
This corresponds to a bandwidth of about 50-60 Mbyte/s on the PCI-Bus.
Also interrupt sharing is an important factor which can lower the overall bandwidth avail-
able.
So it is very wise to set individual interrupts for the host adapter cards if you run into these
problems.
Also be aware that the PC powers the cameras. You must not exceed its powering capabili-
ties.
Use actively powered repeaters or hubs to power the cameras from outside the PC.
Powering the camera is mandatory when you use the 4-pin connectors of the built in
IEE1394 ports of laptops.
Use actively powered repeaters or hubs to power the cameras from outside the PC.