Considerations when using Multiple FireWire Cameras?

Considerations when using Multiple FireWire Cameras?

Considerations when using Multiple FireWire Cameras?
Product:        VisionPro
Platform:        All Platforms
Full Description

What are the important considerations when using multiple FireWire cameras?

Solution

When designing a vision application that will use multiple cameras, the following system configuration options should be considered.

FireWire Adapter

Speed: An IEEE 1394a adapter supports a FireWire bus with 400 Mb/sec of bandwidth while an IEEE 1394b adapter supports a FireWire bus with 800 Mb/sec of bandwidth when used with 1394b-based cameras running in 1394b mode.
×××速度和千兆以太网 没啥区别了，就一点点而已

Note: The 1394b speed is not yet supported by VisionPro.
DMA Channels: All OHCI-based FireWire adapters, the type supported by VisionPro, provide a minimum of 4 DMA channels. With 4 DMA channels, images can be acquired from up to 4 FireWire cameras at the same time. Select an adapter that has at least as many DMA channels as cameras being used for simultaneous acquisition.

PCI interface: Most IEEE 1394a adapters and some IEEE 1394b adapters support the 33-MHz/32-bit PCI interface; some IEEE 1394b adapters are available with the 33-MHz/64-bit PCI interface.
A 33-MHz/32-bit PCI bus provides approximately 80 MB/sec of reliable bandwidth, and a 33-MHz/64-bit PCI bus provides approximately 160 MB/sec of reliable bandwidth.
The 33-MHz/32-bit PCI bus will reliably support one to two 1394a adapters or one1394b adapter.
The 33-MHz 64-bit PCI bus will reliably support up to two 1394b adapters.

FireWire Bus Bandwidth

An IEEE 1394a bus supports image data throughput of 32 MB/sec while an IEEE 1394b FireWire bus supports throughput of 64 MB/sec.
In a multi-camera configuration, make sure not to exceed these maximum rates.
The data rate of a camera in MB/sec can be calculated as follows: (bytes-per-pixel * image-width * image-height * frames-per-second) / (1024 * 1024).

For example, the data rate for a FireWire camera using format 0, mode 5 (640 x 480 mono) at 30 FPS would be: (1 * 640 * 480 * 30) / (1024 * 1024) = 8.79 MB/sec.

PC System

Number of FireWire Adapters: More than one adapter may be used at a time if the number of cameras required by an application exceeds the number of available DMA channels or the available bandwidth on an adapter.

Note: Be careful not to exceed the available PCI bus bandwidth on a PC when using multiple adapters.
PCI Slot Allocation: PCs typically support several bridged PCI buses. The available PCI slots on a PC may be allocated on more than 1 PCI bus. In the case where multiple FireWire adapters are used, knowing the PCI slot allocation might allow taking advantage of additional PCI bandwidth if adapters can be placed in slots that are allocated on separate PCI buses.
PCI Bus Contention: Devices on the same PCI bus as a FireWire adapter will compete for available bus bandwidth. These may include display adapters, network cards, and PCI-based devices integrated onto the PC motherboard for audio, USB, and mass storage. Try to set up PCI-based devices on a PC to limit PCI bus contention for FireWire adapters.
http://help.cognex.com/Content/K ... ion/Acquisition.htm

还不让一次发出来，说是什么危险的连接？？