The BIST test algorithm is a 6N test. Figure 10.1 shows the test flow. The first pass starts from the bottom of the memory to be tested. A fixed value is written into each memory address to be tested and the address is incremented until the top of memory is reached.

The second pass starts from the bottom of the memory to be tested. In the second pass the fixed pattern is checked. If the pattern match fails then the BIST fail flags are set and the test fails. If the pattern match is successful then the inverse pattern is written to each memory address. If the pattern match fails then the BIST fail flags are set and the test fails. The address is incremented until the top of memory is reached.

The third pass starts from the top of memory. The inverse pattern is checked, a fixed value is written into each memory address to be tested. The pattern is then checked. If the pattern match fails on either check, then the BIST fail flags are set and the test fails. The address is decremented until the bottom of the area of memory under test is reached.