A
PPENDIX
A. G
LOSSARY
P
AGE
15
2.4
FireWire Connectors and Multiple Cameras
Each PixeLINK camera has two FireWire connectors (ports), allowing several devices to
The number of cameras that may be managed simultaneously depends on the total
bandwidth and may be limited by power availability (see Section 2.6, below) and the
processing capabilities of the host computer.
The FireWire bus requires that the sum of the packet sizes of the attached cameras be
less than 4800. Packet sizes for cameras operating with 640 × 480 and 1024 × 1280
subwindows are given in Table 2.4 (below).
Table 2.4
Packet Sizes
be daisy-chained. The connectors are identical and either may be used to connect to the
computer. The other can be used to connect to other FireWire devices.
Subwindow Size
Clock
Frequency
(MHz)
640 × 480
1024 × 1280
4
640 1280
6
1280 1280
8
1280 1280
12
1920
2560
16
3200
2560
24
3840
2560
Example
: Based on the FireWire bus only, what is the largest number of
cameras that can be managed simultaneously if each one operates
with 640 × 480 subwindow and an 8 MHz clock frequency?
Solution:
The FireWire packet limit is 4800. From Table 2.4 (above),
the packet size for a 640 × 480 subwindow at 8 MHz is 1280.
75
3
1280
4800
.
=
Therefore, no more than three cameras can be
managed simultaneously at 640 × 480 and 8 MHz.
To confirm:
The total packet size for four cameras is 4 × 1280 = 5120, which
exceeds the FireWire packet limit. The total packet size for three
cameras is 3 × 1280 = 3840, which is less than the limit.
PixeLINK
PL-A630 to PL-A660 Series Cameras
Megapixel FireWire Camera
System Guide
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All Rights Reserved
