ALLIED Vision Technologies Stingray F-504 - Manual (Page 35)

FireWire
STINGRAY Technical Manual V4.4.4
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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).
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.
In addition to common standards shared across manufacturers, a special
Format_7 mode also provided a means by which a manufacturer could offer
special features (smart features), such as:
• higher resolutions
• higher frame rates
• diverse color modes
as extensions (advanced registers) to the prescribed common set.
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.