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Listing 2: Address Bus Test
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datum *
memTestAddressBus(volatile datum * baseAddress, unsigned long nBytes)
{
unsigned long addressMask = (nBytes - 1);
unsigned long offset;
unsigned long testOffset;
datum pattern = (datum) 0xAAAAAAAA;
datum antipattern = (datum) 0x55555555;
/*
* Write the default pattern at each of the power-of-two offsets.
*/
for (offset = sizeof(datum); (offset & addressMask) != 0; offset
<
<
= 1)
{
baseAddress[offset] = pattern;
}
/*
* Check for address bits stuck high.
*/
testOffset = 0;
baseAddress[testOffset] = antipattern;
for (offset = sizeof(datum); (offset & addressMask) != 0; offset
<
<
= 1)
{
if (baseAddress[offset] != pattern)
{
return ((datum *) &baseAddress[offset]);
}
}
baseAddress[testOffset] = pattern;
/*
* Check for address bits stuck low or shorted.
*/
for (testOffset = sizeof(datum); (testOffset & addressMask) != 0;
testOffset
<
<
= 1)
{
baseAddress[testOffset] = antipattern;
for (offset = sizeof(datum); (offset & addressMask) != 0; offset
<
<
= 1)
{
if ((baseAddress[offset] != pattern) && (offset != testOffset))
{
return ((datum *) &baseAddress[testOffset]);
}
}
baseAddress[testOffset] = pattern;
}
return (NULL);
} /* memTestAddressBus() */
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