ALLIED Vision Technologies Guppy F-503 - Manual (Page 219)

How does bandwidth affect the frame rate?
GUPPY Technical Manual V7.1.0
219
How does bandwidth affect the frame
rate?
In some modes the IEEE 1394a bus limits the attainable frame rate. Accord-
ing to the 1394a specification on isochronous transfer, the largest data pay-
load size of 4096 bytes per 125 µs cycle is possible with bandwidth of
400 Mbit/s. In addition, there is a limitation, only a maximum number of
65535 (2
16
-1) packets per frame are allowed (GUPPY F-036: max. number of
800 packets due to the sensor limitation).
The following formula establishes the relationship between the required
Byte_Per_Packet size and certain variables for the image. It is valid only for
Format_7.
If the value for BYTE_PER_PACKET is greater than 4096 (the maximum data
payload), the sought-after frame rate cannot be attained. The attainable
frame rate can be calculated using this formula:
(Provision: BYTE_PER_PACKET is divisible by 4):
ByteDepth based on the following values:
Formula 12: Byte_per_Packet calculation (only Format_7)
Formula 13: Maximum frame rate calculation
Mode Bits/pixel Byte per pixel
Mono8 8 1
RAW8 8 1
Table 90: ByteDepth
BYTE_PER_PACKET frame rate x AOIWidth x AOIHEIGHT x ByteDepth x 125µs =
framerate
max
BYTE_PER_PACKET
AOIWidth x AOIHeight x ByteDepth x 125µs
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