Allied Vision Technologies AVT Stingray Manual de instrucciones descargar pdf (Pagina 24)

FireWire

STINGRAY Technical Manual V2.2.0

FireWire connection capabilities

FireWire can connect together up to 63 peripherals in an acyclic network

structure (hubs). It allows peer-to-peer device communication (between dig-

ital cameras), to take place without using system memory or the CPU.

But even more importantly, a FireWire camera can directly, via direct mem-

ory access (DMA), write into or read from the memory of the computer with

almost no CPU load.

FireWire also supports multiple hosts per bus. FireWire requires only a cable

with the correct number of pins on either end (normally 6 or 9). It is

designed to support plug-and-play and hot swapping. It can supply up to

45 W of power per port at 30 V, allowing high consumption devices to oper-

ate without a separate power cord.

Capabilities of 1394a (FireWire 400)

FireWire 400 (S400) is able to transfer data between devices at 100, 200 or

400 MBit/s data rates. Although USB 2.0 claims to be capable of higher

speeds (480 Mbit/s), FireWire is, in practice, not slower than USB 2.0.

The 1394a capabilities in detail:

• 400 Mbit/s

• Hot-pluggable devices

• Peer-to-peer communications

• Direct Memory Access (DMA) to host memory

• Guaranteed bandwidth

• Multiple devices (up to 45 W) powered via FireWire bus

IIDC V1.3 camera control standards

IIDC V1.3 released a set of camera control standards via 1394a which estab-

lished a common communications protocol on which most current FireWire

cameras are based.

Note

How to extend the size of an isochronous packet up to 11.000

byte at S800:

• see register 0xF1000048, ADV_INQ_3, Max IsoSize [1]

in Table 117: Advanced register: Advanced feature

inquiry on page 257

• see Chapter Maximum ISO packet size on page 280

Caution

While supplying such an amount of bus power is clearly a

beneficial feature, it is very important not to exceed the

inrush current of 18 mJoule in 3 ms.

Higher inrush current may damage the Phy chip of the

camera and/or the Phy chip in your PC.

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Allied Vision Technologies AVT Stingray Manual de instrucciones Pagina 24