User guide

66 www.xilinx.com System Generator for DSP User Guide
UG640 (v 12.2) July 23, 2010
Chapter 1: Hardware Design Using System Generator
The example contains two additional accumulator subsystems with MCode blocks using
the same M-function, but different parameter settings to accomplish different accumulator
implementations.
FIR Example and System Verification
This example shows how to use the MCode block to model FIRs. It also shows how to do
system verification with the MCode block.
The model contains two FIR blocks. Both are modeled with the MCode block and both are
synthesizable. The following are the two functions that model those two blocks.
function y = simple_fir(x, lat, coefs, len, c_nbits, c_binpt, o_nbits,
o_binpt)
coef_prec = {xlSigned, c_nbits, c_binpt, xlRound, xlWrap};
out_prec = {xlSigned, o_nbits, o_binpt};
coefs_xfix = xfix(coef_prec, coefs);
persistent coef_vec, coef_vec = xl_state(coefs_xfix, coef_prec);
persistent x_line, x_line = xl_state(zeros(1, len-1), x);
persistent p, p = xl_state(zeros(1, lat), out_prec, lat);
sum = x * coef_vec(0);
for idx = 1:len-1
sum = sum + x_line(idx-1) * coef_vec(idx);
sum = xfix(out_prec, sum);
end
y = p.back;
p.push_front_pop_back(sum);
x_line.push_front_pop_back(x);
function y = fir_transpose(x, lat, coefs, len, c_nbits, c_binpt,
o_nbits, o_binpt)
coef_prec = {xlSigned, c_nbits, c_binpt, xlRound, xlWrap};
out_prec = {xlSigned, o_nbits, o_binpt};
coefs_xfix = xfix(coef_prec, coefs);
persistent coef_vec, coef_vec = xl_state(coefs_xfix, coef_prec);
persistent reg_line, reg_line = xl_state(zeros(1, len), out_prec);
if lat <= 0