{	    

	Mu-Law Expansion routine.	

	Calling Parameters
    R0 = Input 8-bit compressed value

	Result Registers
    R0 = Expanded linear value

	Altered Registers
    R0,  R12, R13, R15

	Cycle Time
    15 Cycles

    The Applications Library
    Gordon A. Sterling  3/20/90

}

#include "asm_glob.h"

.SEGMENT/PM   Assembly_Library_Code_Space;

.GLOBAL	uexpand;

uexpand:	R12=H#FF;			{Mask unwanted bits}
		R15=R0 AND R12;
		R15=R12 XOR R15;		{Invert bits}
		R12=H#70;
		R13=R12 AND R15;		{Isolate segment bits}
		R0=R13 XOR R15;			{Remove segment bits}
		R12=H#FFFFFF80;
		R15=R0+R12;
		IF LT JUMP posval (DB);		{Determine sign}
		R12=33;
		R13=LSHIFT R13 BY -4;		{Shift segment bits to LSBs}

negval:		R0=R15+R15;
		RTS (DB), R0=R0+R12;		{Add segment offset}
		R0=ASHIFT R0 BY R13;		{Position bits}
		R0=R12-R0;			{Remove segment offset}

posval:		R0=R0+R0;
		RTS (DB), R0=R0+R12;		{Add segment offset}
		R0=ASHIFT R0 BY R13;		{Position bits}
		R0=R0-R12;

.ENDSEG;