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Firewire connection capabilities, Capabilities of 1394a (firewire 400), Iidc v1.3 camera control standards – ALLIED Vision Technologies Pike F-1600 User Manual

Page 37

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FireWire

PIKE Technical Manual V5.1.2

37

FireWire connection capabilities

FireWire can connect together up to 63 peripherals in an acyclic network struc-
ture (hubs). It allows peer-to-peer device communication (between digital
cameras), to take place without using system memory or the CPU.

But even more importantly, a FireWire camera can directly, via direct memory
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 can supply up
to 45 W of power per port at 30 V, allowing high consumption devices to operate
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 153: Advanced register: Advanced feature inquiry

on page 331

see Chapter

Maximum ISO packet size

on page 355

Caution

While supplying such an amount of bus power is clearly a ben-
eficial 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 cam-
era and/or the Phy chip in your PC.

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