Datasheet

writing a '1' in STATUSA.FAIL to resume. Prior to resuming, user can read the DATA and

ADDR registers to locate the fault.

4. Locating Faults

If the test stops with STATUSA.FAIL set, one or more bits failed the test. The test stops at the first

detected error. The position of the failing bit can be found by reading the following registers:

– ADDR: Address of the word containing the failing bit

– DATA: contains data to identify which bit failed, and during which phase of the test it failed.

The DATA register will in this case contains the following bit groups:

Figure 13-6. DATA bits Description When MBIST Operation Returns an Error

Bit

phase

bit_index

31 30

29 28

26 25

22 21

20 19 18

12 11

10 9 8

6 5

2 1

• bit_index: contains the bit number of the failing bit

• phase: indicates which phase of the test failed and the cause of the error, as listed in the following

table.

Table 13-4. MBIST Operation Phases

Phase Test actions

0 Write all bits to zero. This phase cannot fail.

1 Read '0', write '1', increment address

2 Read '1', write '0'

3 Read '0', write '1', decrement address

4 Read '1', write '0', decrement address

5 Read '0', write '1'

6 Read '1', write '0', decrement address

7 Read all zeros. bit_index is not used

Table 13-5. AMOD Bit Descriptions for MBIST

AMOD[1:0] Description

0x0 Exit on Error

0x1 Pause on Error

SAM D21 Family

DSU - Device Service Unit

Datasheet Complete

DS40001882D-page 82