ALLIED Vision Technologies Guppy PRO F-503 - Manual (Page 90)

Camera interfaces
Guppy PRO Technical Manual V4.0.0
88
Pixel data
Pixel data are transmitted as isochronous data packets in accordance with
the 1394 interface described in IIDC V1.31. The first packet of a frame is
identified by the 1 in the sync bit (sy) of the packet header.
• The video data for each pixel are output in either 8-bit or 14-bit format
(Packed 12-Bit Mode: 12-bit format).
• Each pixel has a range of 256 or 16384 (Packed 12-Bit Mode: 4096)
shades of grey.
• The digital value 0 is black and 255 or 16383 (Packed 12-Bit Mode:
4095) is white. In 16-bit mode the data output is MSB aligned.
Field Description
data_length Number of bytes in the data field
tg Tag field
shall be set to zero
channel Isochronous channel number, as programmed in the iso_channel
field of the cam_sta_ctrl register
tCode Transaction code
shall be set to the isochronous data block packet tCode
sy Synchronization value (sync bit)
This is one single bit. It indicates the start of a new frame.
It shall be set to 0001h on the first isochronous data block of a frame,
and shall be set to zero on all other isochronous blocks
Video data payload Shall contain the digital video information
Table 33: Description of data block packet format
0-7 8-15 16-23 24-31
data_length tg channel tCode sy
header_CRC
Video data payload
data_CRC
Table 32: Isochronous data block packet format. Source: IIDC V1.31
sync bit