Video Port Features

To handle video streams, processors must have a suitable interface that can maintain a high data transfer rate into and out of the part. Some processors accomplish this through an FPGA and/or FIFO connected to the processor's external memory interface. Typically, this device will negotiate between the constant, relatively slow stream of video into and out of the processor, and the sporadic but speedy bursting nature of the external memory controller.

However, there are problems with this arrangement. For example, FPGAs and FIFOs are expensive, often costing as much as the video processor itself. Additionally, using the external memory interface for video transfer steals bandwidth from its other prime use in these systems moving video buffers back and forth between the processor core and external memory.

Therefore, a dedicated video interface is highly preferable for media processing systems. On Blackfin processors, this is the Parallel Peripheral Interface (PPI). The PPI is a multifunction parallel interface that can be configured between 8 and 16 bits in width. It supports bidirectional data flow and includes three synchronization lines and a clock pin for connection to an externally supplied clock. The PPI can gluelessly decode ITU-R BT.656 data and can also interface to ITU-R BT.601 video streams. It is flexible and fast enough to serve as a conduit for high-speed analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). It can also emulate a host interface for an external processor. It can even act as a glueless TFT-LCD controller.