band pass FIR filter and weird response

I just modelled a bandpass filter without scaling down and found out

it is possible to get a dc value as high as your 65534:

h = fir1(79,[.1 .2]);

h = round(h*1024);

x = [zeros(1,100) -32768 ones(1,1000)*32767];

y1 = filter(h,1,x);

y2 = round(y1/1024);

you will see y1 has a high residual dc that is scaled down by 1024 in y2.

The actual value depends on your filter unity gain and filter's dc removal.