meas_ber :
A primitive for measuring the bit-error rate of a data stream.

The meas_ber primitive measures the bit-error rate of a data stream in by comparing it either with the external reference data stream in_ref (mode=”ext” or “in”) or with an internal PRBS reference (mode=”int” or “prbs”). In case of using an internal PRBS reference, the parameter length defines the LFSR length N, generating a pseudo-random bit sequence with a length of 2^N-1. The value range of length is 3~128 (default: 7).

The parameter trig_mode defines whether the inputs in and in_ref are sampled at the positive edge (1), negative edge (-1), or both edges (0) of the input clk. By default, the inputs are sampled at the negative edge of clk (-1), assuming the data transitions are aligned with the positive edges of clk. The parameters start and stop define when the measurement begins and ends, respectively.

Input/Output Terminals

Name	I/O	Type	Description
bit_err	output	reg	bit error indicator
prb_err	output	real	bit error probability
in	input	xbit	input signal
in_ref	input	xbit	reference signal
clk	input	xbit	clock signal

Parameters

Name	Type	Default	Unit	Description
mode	string	“ext”	None	reference source
length	integer	7	None	reference LFSR length
trig_mode	integer	-1	None	triggering mode
start	real	0.0	seconds	abs. time to start measurement
stop	real	-1.0	seconds	abs. time to stop measurement