BitFlow Cyton-CXP, Hardware Reference Manual

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General Description The Cyton-CXP
CYT-1-6 BitFlow, Inc. Version A.0
1.3.1 Video Data
Three types of packets are sent from the camera on the CoaXPress downlink: Video
(stream) data, control (command) packets and Trigger packets. Video packets contain
video information (pixels). Control packets contain commands and response. The
control packets are use to read/write from/to the cameras internal register space. Trig-
ger packets are used to send triggers to the host.
Packets containing video data are sent to a stream assembler. The stream assembler
builds up lines of video data which are then sent to the acquisition and control logic
(see Figure 1-2). From this point on the Cyton-CXP works very similar to all of BitFlow’s
frame grabbers. The acquisition circuit determines which pixels of which lines of
which frames are to be acquired. The correct pixels are then sent to a FIFO, the output
of which read by the DMA engine. The DMA engine then DMAs the data to host
memory.
CoaXPress cameras can output video on multiple links simultaneously. There is no
correlation between parts of the sensor and CXP links (like there is between sensor
taps and Camera Link taps). Any part of any line can be sent on any link in a multi-link
camera. The stream assembler must decode the packet headers and assemble raster
format lines.
1.3.2 Command and Control Packets
The second type of packet coming from the camera is a control packet. When the
board sees a control packet, it unwraps the packet and sends the contents into a con-
trol data FIFO. The host then reads and decodes this FIFO. Currently (as of CoaXPress
specification 1.1) control packets are synchronous. This means that the camera will
only send a control packet in response to a control packet sent from the host. For this
reason, software can be fully under control of the control packets sent from the cam-
era. It is not necessary to have an interrupt driven control packet circuit as there is for
serial communications in Camera Link. However, this may change with future revision
os the CoaXPress specification.
1.3.3 CXP Triggers
The third type of packet the Cyton-CXP handles are the trigger packets. The camera
can send a trigger packet at any time. The Cyton-CXP maps the trigger packet into the
board’s trigger circuitry. It is one possible source for the internal trigger signal.
1.3.4 Up Link
CoaXPress provides a high speed uplink to control the camera. The uplink is also
packet based like the downlink. However, the uplink only supports two types of pack-
ets, control and Trigger. These packets are similar to the packets in the downlink. For
control packets, the BitFlow software builds up the packet in the board’s outgoing
control packet FIFO. Once the packet is fully built, a single bit sends the packet to the