AVIIVA® EM1
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1043D - AVIIVA EM1 –04/11
e2v semiconductors SAS 2011
6.4
Packet_Resend mechanism
The AVIIVA EM1 camera embeds a dedicated memory to store the data frames in order to be able to
resend packets when requested by the host driver.
If the host driver detects that one or multiple packets are missing then resend request commands are
sent to the camera. This feature can be enabled or disabled depending on the GEV driver used. But this
feature is always enabled in the AVIIVA EM1 camera.
In the AVIIVA EM1 camera the sensor stream has a higher priority than the packet_resend channel.
This means that when the line frequency increases the time available for packet resend decreases. The
AVIIVA EM1 camera has a 512Mbit memory let say 8192 packets of 8192 bytes.
If the host driver requests a single packet it sends a request command with the block_ID and the
packet_ID. If it requests multiple following packets it sends a request command with the block_ID, the
packet_ID of the first missing packet and the packet_ID of the last missing packet. The camera resend
the packets provided there are still in its memory. If not the camera answers the requests with an
extended status code (if enabled) indicating why the packets can’t be resend.
