Add real ADSP-2191 assembly examples + open21xx assembler test

examples/adsp-2191_iir/ADSP-2191_IIR.txt

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+****************************************************************************
+
+IIR.asm      Infinite impulse response filter (IIR)
+
+Analog Devices, Inc.
+DSP Division
+Three Technology Way
+P.O. Box 9106
+Norwood, MA 02062
+
+23-JUNE-2001 BJM
+
+This directory contains an example ADSP-2191, single-core Infinite 
+Impulse Response (IIR) filter.  
+The IIR code uses coefficients, in an ordered array and applies them to
+the filter. A detailed discussion of the IIR algorithm can be found 
+in the source header comments of "IIR.ASM".
+
+Files contained in this directory:
+
+iir.asm      		ADSP-2191 source for an example IIR filter
+iir_test.asm      	ADSP-2191 source to call iir.asm
+adsp-2191.ldf     	Linker description file for the IIR example
+iir.dpj          	The VDSP project file for the IIR example.
+inreal_256.dat         	Input data for IIR example in 1.15 format.
+coefs_hex.dat    	Coefficients for IIR example in 1.15 format.
+ _________________________________________________________________
+
+CONTENTS
+
+I.    FUNCTION/ALGORITHM DESCRIPTION
+II.   IMPLEMENTATION DESCRIPTION
+III.  DESCRIPTION OF INPUT DATA         
+
+I. FUNCTION/ALGORITHM DESCRIPTION
+
+The IIR filter code executes a canonical form (also called direct form II)
+realization structure.  The equation of the canonical form is
+    
+    w(n)=x(n) + b1*w(n-1) + b2*w(n-2)
+    y(n)=w(n) + a1*w(n-1) + a2*w(n-2)
+
+The input sample is x(n) and the output is y(n).  The term w(n) is the
+intermediate value; w(n-1) is the previous value and w(n-2) the one before
+that.  The variables a and b are the coefficients for the filter.
+
+This example of canonical equation uses a variant that limits the summation
+in the canonical form to two.  This type of IIR is called a biquad and is a 
+second order filter.  Higher order filters can be achieved by cascading several
+sections of biquads together.
+
+
+II.   IMPLEMENTATION DESCRIPTION
+
+The assembly language module IIR_TEST.ASM initializes the input and 
+coefficient buffers and then calls IIR.ASM.   
+     
+The first buffer declared, INBUF, is N_samp sample locations long.
+
+The next buffer declared, OUTBUF, is also N_samp samples long, and stores the 
+output of the filter.
+
+DLINE is the third buffer declared.  This buffer holds the delay line for each
+biquad.  That is w(n-1) and w(n-2) for each biquad section of the filter.  Since
+there are two past intermediate vales for each stage of the biquad, the length of
+this buffer is twice as long as the stages.
+
+The coefficient buffer, COEFS, contains the IIR filter coefficients.  The 
+coefficients are typically generated by a filter 
+design software package.
+
+The linker descriptive file is ADSP-2191.LDF, which describes the hardware in 
+terms of memory spaces and peripherals.
+
+Because there is no data dependency between DSP cores, it is possible 
+to do perform an IIR in DSP core 1, while also performing an IIR in DSP core 2 
+on separate input data, using different coefficients.
+
+
+III.  DESCRIPTION OF INPUT DATA
+
+1. INPUT SAMPLES:
+-----------------
+This IIR routine expects input data which conforms to the following criteria:
+
+Generate input data such that an array of input fixed point values are 
+in 1.15 format, with the data being arranged in the following order:
+
+INPUT DATA
+
+indata(0)      
+indata(1)      
+indata(2)      
+indata(3)      
+etc...         
+
+
+2. COEFFICIENT DATA:
+-----------------------
+This IIR routine expects [Biquad_secs*4] fixed point values to be used as coefficients.
+
+
+COEFFICIENT DATA
+
+A2(0)
+A1(0)
+B2(0)
+B1(0)
+... 
+... 
+... 
+
+
+
+