The STi3520 requires minimal support from an external microcontroller, which is mainly required to initialise the video decoder at the start of every picture. Separate audio and video data streams are input through the 8-bit data port. Time stamps are detected and made available to the microcontroller for the managementof audio/videosynchronization. User-defined bitmaps may be superimposedon the displayed picture through use of the on-screen display function. These bitmaps are written directly into the DRAM memory by the microcontroller. Undetected bitstream errors which would cause decoder errors activate the error concealment functions.