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FireWire
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
inquiry
• see Chapter
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.
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.
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.
Table 124: Advanced register: Advanced feature
on page 269
Maximum ISO packet size
on page 292
PIKE Technical Manual V4.1.0
27
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