The sequence of the 2-bit, watchdog answer-counter is as follows for each counter value:
- WD_ANSW_CNT[1:0] = 2‘b11:
- The watchdog calculates the reference Answer-3.
- A write access occurs. The MCU writes the Answer-3 byte in WD_ANSWER[7:0].
- The watchdog compares the reference Answer-3 with the Answer-3 byte in WD_ANSWER[7:0].
- The watchdog decrements the WD_ANSW_CNT[1:0] bits to 2b‘10 and sets the WD_ANSW_ERR status bit to 1 if the Answer-3 byte was incorrect.
- WD_ANSW_CNT[1:0] =
2b‘10:
- The watchdog calculates
the reference Answer-2.
- A write access occurs.
The MCU writes the Answer-2 byte in WD_ANSWER[7:0].
- The watchdog compares the
reference Answer-2 with the Answer-2 byte in WD_ANSWER[7:0]..
- The watchdog decrements
the WD_ANSW_CNT[1:0] bits to 2b‘01 and sets the WD_ANSW_ERR status bit
to 1 if the Answer-2 byte was incorrect.
- WD_ANSW_CNT[1:0] = 2b‘01:
- The watchdog calculates the reference Answer-1.
- A write access occurs. The MCU writes the Answer-1 byte in WD_ANSWER[7:0].
- The watchdog compares the reference Answer-1 with the Answer-1 byte in WD_ANSWER[7:0]..
- The watchdog decrements the WD_ANSW_CNT[1:0] bits to 2b‘00 and sets the WD_ANSW_ERR status bit to 1 if the Answer-1 byte was incorrect.
- WD_ANSW_CNT[1:0] = 2b‘00:
- The watchdog calculates the reference Answer-0.
- A write access occurs. The MCU writes the Answer-0 byte in WD_ANSWER[7:0].
- The watchdog compares the reference Answer-0 with the Answer-0 byte in WD_ANSWER[7:0].
- The watchdog sets the WD_ANSW_ERR status bit to 1 if the Answer-0 byte was incorrect.
- The watchdog starts a new watchdog sequence and sets the WD_ANSW_CNT[1:0] to 2‘b11’.
The MCU needs to clear the bit by writing a '1' to the WD_ANSW_ERR bit.
Table 8-9 Set of Questions and
Corresponding Answer-Bytes Using the Default Setting of WD_QA_CFG
Register
WD QUESTION |
ANSWER-BYTES (EACH BYTE TO BE WRITTEN INTO
WD_ANSWER[7:0]) |
ANSWER-3 |
ANSWER-2 |
ANSWER-1 |
ANSWER-0 |
WD_QUESTION[3:0] |
WD_ANSW_CNT
[1:0] = 2’b11 |
WD_ANSW_CNT
[1:0] = 2’b10 |
WD_ANSW_CNT
[1:0] = 2’b01 |
WD_ANSW_CNT
[1:0] = 2’b00 |
0x0 |
FF |
0F |
F0 |
00 |
0x1 |
B0 |
40 |
BF |
4F |
0x2 |
E9 |
19 |
E6 |
16 |
0x3 |
A6 |
56 |
A9 |
59 |
0x4 |
75 |
85 |
7A |
8A |
0x5 |
3A |
CA |
35 |
C5 |
0x6 |
63 |
93 |
6C |
9C |
0x7 |
2C |
DC |
23 |
D3 |
0x8 |
D2 |
22 |
DD |
2D |
0x9 |
9D |
6D |
92 |
62 |
0xA |
C4 |
34 |
CB |
3B |
0xB |
8B |
7B |
84 |
74 |
0xC |
58 |
A8 |
57 |
A7 |
0xD |
17 |
E7 |
18 |
E8 |
0xE |
4E |
BE |
41 |
B1 |
0xF |
01 |
F1 |
0E |
FE |