Listing 1 for DI #2313:
"RISC [lmu]P implements fast FIR filter"
by Sorin Zarnescu, NEC Electronics, Santa Clara, CA

************************************************************************

 .data
 .align  4
 .global  M1,M2,M3,M4,New


 c1 		.set		0x00; coef 1
 c2		.set		0x10; coef 2
 c3		.set		0x20; coef 3
 c4		.set		0x30; coef 4
 M1		.hword		0x0010        	; first sample		
 M2		.hword		0x0020       	; second sample
 M3		.hword		0x0030        	; third sample
 M4		.hword		0x0040       	; fourth sample
 New    		.hword		0x0050		;new sample -  written by the interrupt routine



.text
.align 4


ld.h		M1[r0],r1; load first sample into register 1
ld.h		M2,[r0]r2; load second sample into register 2
muli		c1,r1,r1    ;(coef 1 x sample 1) --> accumulator
st.h		r1,M1[r0] ; store first sample into the second memory location
ld.h		M3[r0],r3; load third sample into register 3
maci		c2,r2,r1    ; (coef 2 x sample 2) + accumulator --> accumulator
st.h		r2,M3[r0] ; store second sample into third memory location
ld.h		M4[r0],r4 ; load lst sample
maci		c3,r3,r1    ; (coef 3 x sample 3) + accumulator --> accumulator
st.h		r3,M4[r0] ; store third sample into last memory location
maci		c4,r4,r1; (coef 4 x sample 4) + accumulator --> accumulator