Abstract
Some GMSL1 (1.5-3Gbps) devices are intended for camera applications. These devices have a double speed interface clock mode (DBL) to allow 2 camera samples per pixel, a technique used for YUV format data or multiple exposures per pixel. All GMSL devices can be intermixed, here we explain what happens when using the DBL mode in one part and it is not available in the other.
Content
GMSL1 transmits video data in frames with up to 24 user data bits, and control signals such as HS and VS. One frame represents one pixel. DBL doubles the pixel clock speed and takes 2 samples per frame, each with up to 12 user bits and control signals, each 12-bit sample has its own VS and HS, 2 samples are put into 1 frame. When a deserializer without DBL mode is connected to a serializer using DBL, the data is output as 24 user bits plus 2 each of HS and VS, and it is the responsibility of the connected video processor to seperate the 2 samples. When a serializer without DBL is connected to a serializer without it, the deserializer will split the video data into 2 samples, and it is the responsibility of the video processor to recombine the samples. An additional issue that needs to be considered, is that the order of the 2 samples in a frame can be different from the video source, so 1 frame may contain samples 1 and 2, or samples 2 and 3. The video processor also needs to resolve this, normally by looking at the timing of the HS and VS signals in the 2 samples.