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adat receiver: Overview Details Name: adat_optical_feed_forward_receiver Created: 25-Jul-2008 07:20:31 Updated: 25-Jul-2008 14:49:04 CVS: no files in cvs Other project properties Category :: Communication controller Language :: VHDL Development status :: Alpha Project maintainers Danny Witberg Statistics view Description This is a feed forward receiver for an ADAT lightpipe optical datastream. This type of multichannel audio connection is widely used in professional digital recording studios. It consists of eight 24 bit wide audio words, at a sample rate (wordclock) of 32kHz, 44,1kHz or 48kHz. It can double the sample rate at the cost of half the number of channels, this is called S-MUX (not supported yet). There are 4 user bits to carry extra data (MIDI, S-MUX indicator, timecode and spare). ADAT streams are encoded with NRZI coding, meaning a change in the ADAT stream is a "1", with no change a "0" is sent. The receiver needs one extra input besides the ADAT stream: Any stable clock (m_clk) between 80MHz and 160MHz should work. One instance is used: a 12x8 multiplier with the 12 MSB's output. Compiled for an Altera Cyclone II the design uses 706LE's and 2 embedded 9 bit multipliers. Features feed forward: other than a non-related clock signal, only the ADAT data stream is required. outputs the 8 audio words on a databus. regenerates the wordclock from the received stream. outputs the user bits as seperate pins. adapts to speed changes. should (!) lock on to the stream in a matter of seconds. Status preliminary VHDL code written testbench completed simulation of design in progress todo: try the design in an FPGA. comment the code. Some ADAT frames in simulation Frame delimiter closeup