.module do_DC_and_brev;
.const sqrt2div2=h#5A82;
.external tmp;
.entry DC_AND_BREV;

DC_AND_BREV:    mx0=dm(tmp);
DCterm:         my0=sqrt2div2;
                mr=mx0*my0(rnd);        { calculate DC term using sqrt(2)/2 }
                dm(tmp)=mr1;
descramble:     i0=h#0007;      { h#0007 = bitrev(^tmp) when ^tmp=h#3800 }
                m0=1024;        { bitrev modifier = 16384/N = 1024 }
                cntr=16;
                ena bit_rev;
                do unbrev until ce;
                   ax0=dm(i0,m0);       { read from bit-reversed tmp buffer }
unbrev:            dm(i5,m5)=ax0;       { write to normal ordered x buffer }
                dis bit_rev;
                rts;
.endmod;