prbs_gen :
A digital PRBS generator.

The prbs_gen primitive generates a pseudo-random bit sequence (PRBS) with a length of 2^N-1 to an xbit-typed output when triggered by the input trig. The LFSR length N is set by the parameter length. The valid range of length is 3~128 (default: 7).

The primitive can also generate a parallel stream of M-bit pseudo-random sequences, where the bit-width M is set by the parameter width. The parameter seq_mode defines whether the parallel stream is a MSB-first sequence (1) or LSB-first sequence (0). Its default value is 1 (MSB-first).

The parameter trig_mode defines whether the primitive is triggered by the positive edge (1), negative edge (-1), or both edges (0) of the input trig (default: 1).

Input/Output Terminals

Name	I/O	Type	Description
out	output	xbit	signal output
trig	input	xbit	trigger input

Parameters

Name	Type	Default	Unit	Description
length	int	7	None	LFSR length
width	int	1	None	output width
seq_mode	int	0	None	sequence mode
trig_mode	int	1	None	triggering mode