Block Sync - Xilinx RocketIO X User Manual

Block Level Functions

Block Sync

Normal Operation
This block sync design works hand-in-hand with the commaDet block. The commaDet
takes as input 32 bits of scrambled and unaligned data from the PMA. It then sends to the
block sync the 2-bit sync header, or what it thinks is the sync header based on the current
tag value. It asserts test_sh which tells the block sync to test the value of the sync header.
The block sync analyzes the sync header and if it is valid, increments the sh_cnt counter.
If the sync header is not a legal value, sh_cnt is incremented as well as the counter
sh_invalid_cnt, and then bit_slip is asserted for one clock. The bit slip signal feeds
back to the commaDet block and tells it to shift the barrel shifter by one bit. This process of
slipping and testing the sync header repeats until block lock is achieved.
RocketIO™ X Transceiver User Guide
UG035 (v1.5) November 22, 2004
www.xilinx.com
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