Listing 2-There will be interesting surprises in the C code operation if the 21K circular buffer hardware is left activated.
C code segment
int values[10];
int sum = 0;
int *pt = values;
for (count = 0; count < 3; count++)
sum = sum +*pt++;
21K code segment
.segment/dm seg_dmda;
.var VALUES[10];
.endseg;
.segment/pm seg_pmco;
// Some where else in the code the 21K 
// circular buffer hardware gets left activated
B4 = VALUES;
L4 = 2;
// Same code as before
// Clear the sum variable
R0 = 0;
// Setup the pointer to the array
I4 = VALUES; 
// Set up address modify constant
M4 = 1;
// Calculate the sum
R1 = dm(I4, M4);	// Fetch
R0 = R0 + R1;	// and add
R1 = dm(I4, M4);	// Fetch
R0 = R0 + R1;	// and add
// I4 is incremented, and 
// then adjusted by the 
// circular buffer hardware
// to point back to VALUES[0]
R1 = dm(I4, M4);	// Fetch
R0 = R0 + R1;	// and add
// I4 pointing to VALUES[1]

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