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# mach: bfin
// GENERIC PN SEQUENCE GENERATOR
// Linear Feedback Shift Register
// -------------------------------
// This solution implements an LFSR by applying an XOR reduction
// function to the 40 bit accumulator, XORing the contents of the
// CC bit, shifting by one the accumulator, and inserting the
// resulting bit on the open bit slot.
// CC --> ----- XOR--------------------------
// | | | | | |
// | | | | | |
// +------------------------------+ v
// | b0 b1 b2 b3 b38 b39 | in <-- by one
// +------------------------------+
// after:
// +------------------------------+
// | b1 b2 b3 b38 b39 in |
// +------------------------------+
// The program shown here is a PN sequence generator, and hence
// does not take any input other than the initial state. However,
// in order to accept an input, one simply needs to rotate the
// input sequence via CC prior to applying the XOR reduction.
.include "testutils.inc"
start
loadsym P1, output;
init_r_regs 0;
ASTAT = R0;
// load Polynomial into A1
A1 = A0 = 0;
R0.L = 0x1cd4;
R0.H = 0xab18;
A1.w = R0;
R0.L = 0x008d;
A1.x = R0.L;
// load InitState into A0
R0.L = 0x0001;
R0.H = 0x0000;
A0.w = R0;
R0.L = 0x0000;
A0.x = R0.L;
P4 = 4;
LSETUP ( l$0 , l$0end ) LC0 = P4;
l$0: // **** START l-LOOP *****
P4 = 32;
LSETUP ( m$1 , m$1 ) LC1 = P4; // **** START m-LOOP *****
m$1:
A0 = BXORSHIFT( A0 , A1, CC );
// store 16 bits of outdata RL1
R1 = A0.w;
l$0end:
[ P1 ++ ] = R1;
// Check results
loadsym I2, output;
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x5adf );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x2fc9 );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0xbd91 );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x5520 );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x80d5 );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x7fef );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x34d1 );
R0.L = W [ I2 ++ ]; DBGA ( R0.L , 0x915c );
pass
.data;
output:
.dw 0x0000
.dw 0x0000
.dw 0x0000
.dw 0x0000
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