Add real ADSP-2191 assembly examples + open21xx assembler test

examples/adsp-2191_viterbi_decoder/ADSP-2191_Viterbi_Decoder.txt

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+****************************************************************************
+
+Viterbi.asm      Soft Decision GSM Viterbi Decoder
+
+Analog Devices, Inc.
+DSP Division
+Three Technology Way
+P.O. Box 9106
+Norwood, MA 02062
+
+21-JUNE-2001 BJM
+
+This directory contains an example ADSP-2191 single-core subroutine 
+that implements a soft decision half-rate, soft-decision, GSM Viterbi decoder.
+
+Files contained in this directory:
+
+VITERBI.dpj			VisualDSP project file
+VITERBI.asm			ADSP-2191 source for Viterbi
+ADSP-2191.ldf			Linker description file 
+GSM_REC.dat			Soft decision data for Viterbi
+ _________________________________________________________________
+
+CONTENTS
+
+I.    FUNCTION/ALGORITHM DESCRIPTION
+II.   IMPLEMENTATION DESCRIPTION
+III.  DESCRIPTION OF INPUT DATA         
+
+I. FUNCTION/ALGORITHM DESCRIPTION
+
+The project Viterbi.dpj contains an implementation of a single-core
+subroutine that implements a half-rate, soft-decision, GSM Vitertbi decoder.  
+
+II.   IMPLEMENTATION DESCRIPTION
+
+1. METRIC UPDATE:
+-----------------
+The metric update section accumulates branch distance metrics into path metrics.
+The lowest path metric at the end of processing is considered to denote the 
+path most likely to contain the correct decoding of the input. 
+
+Each element of the state_trans[] array represents a state transition.  
+Each of the 16-bits in an element of state_trans[] represents one of the
+16 possible new states, and indicates which of two possible states
+is the most likely previous state.
+
+2. TRACE BACK:
+--------------
+The traceback traces back through the state_trans[] array.  Starting
+with a new state, the bits of "state" are rotated to compute the
+position of the bit in the current state_trans[] array element that 
+represents this new state.  This bit indicates which state was previous.  
+We update the state to the previous state using this bit. 
+
+During any state transition, the most significant of the four bits in
+"state" is the most recent input bit to the convolutional encoder.
+This is the bit which is added to the output of the decoder.
+
+III.  DESCRIPTION OF INPUT DATA
+
+1. INPUT SAMPLES:
+-----------------
+The Viterbi decoder routine expects input data which conforms to the following criteria:
+
+The class 1 bits are encoded with the 1/2 rate convolutional code defined by 
+the polynomials:
+
+G0 = 1 + D3+ D4
+G1 = 1 + D + D3+ D4
+
+Encoded outputs are transmitted as signed antipodal analog signals.  They are received at 
+the decoder and quantized.  The quantized number is represented in a 2's
+compliment giving the range of -8 to 7.  The process of quantizing a binary analog signal
+with a multi-bit qunatizer is called soft decision.  This soft decision is stored in the 
+array 'SOFT_DEC_INPUT'.
+
+
+
+