{
	A-Law expansion routine.

	Calling Parameters
    R0 = Compressed 8-bit Input Value

	Result Registers
    R0 = Linear value

	Altered Registers
    R0, R1, R12, R13, R15;

	Cycles Time
    19 Cycles

    Version 0.01    8/10/90	Gordon A. Sterling
}

#include "asm_glob.h"

.SEGMENT/PM	Assembly_Library_Code_Space;

.GLOBAL	    aexpand;

aexpand:	R12=H#FF;		{Mask unwanted bits}
		R15=R0 AND R12;
		R12=H#55;		{Invert odd bits}
		R15=R12 XOR R15;	{Invert bits}
		R13=LSHIFT R15 BY -4;	{Isolate segment}
		R13=BSET R13 BY 3;	{Always set sign bit}
		R12=32;		
		R1=9;
		R13=R13-R1;		{Determine sight value}
		IF LT R12=R12-R12;	{Dont OR MSB bit}
		IF EQ R13=R13-R13;	{No less then zero bits}
		R1=LSHIFT R15 BY 28;	{Isolate interval}
		R1=BSET R1 BY 27;	{Set LSB of interval}
		R1=LSHIFT R1 BY -27;	{Shift interval into bottom}
		R1=R1 OR LSHIFT R12 BY 0;{Add MSB if necessary}
		R0=LSHIFT R1 BY R13, R1=R0;{Position interval}
		RTS (DB);
		BTST R1 BY 7;		{Check sign of input}
		IF SZ R0=-R0;		{Invert output}

.ENDSEG;