ALLIED Vision Technologies Guppy PRO F-503 - Manual (Page 201)

How does bandwidth affect the frame rate?
Guppy PRO Technical Manual V4.0.0
199
How does bandwidth affect the frame
rate?
In some modes the IEEE 1394b bus limits the attainable frame rate. Accord-
ing to the 1394b specification on isochronous transfer, the largest data pay-
load size of 8192 bytes per 125 µs cycle is possible with bandwidth of
800 Mbit/s. In addition, there is a limitation, only a maximum number of
65535 (2
16
-1) packets per frame are allowed.
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 8192 (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):
Note

Certain cameras may offer, depending on their settings in
combination with the use of AVT FirePackage higher packet
sizes.
Consult your local dealer's support team, if you require addi-
tional information on this feature.
Formula 19: Byte_per_Packet calculation (only Format_7)
Formula 20: Maximum frame rate calculation
BYTE_PER_PACKET frame rate AOI_WIDTH

AOI_HEIGHT

ByteDepth

125µs
 =
frame rate
BYTE_PER_PACKET
AOI_WIDTH AOI_HEIGHT

ByteDepth

125µs

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