Q&A Token Response Bits Table

The token response (or feedback) includes token values and a response bit field.

There are eight response bits for each byte-write to the watchdog timer. The response bit is calculated using a modulus-2 based arithmetic to get a single bit result (example: 1 ⊕ 1 ⊕ 1 = 1).

The 4-bit feedback value is from the Token_FB [FDBK] bit field.
The 4-bit token value is from the Token_FB [TVAL] bit field.
The 2-bit count value is from the Enable_and_Status [ACNT] bit field.

Software writes the 8-bit response value in proper succession to the Token_Resp [ANS] bit field.

Table 1. SWDT Q&A Token Value, Part A
Token	Token value written to SWDT.Token_FP [9:8]
Token	00	01	10	11
Token[0]	LFSR[1] ⊕ Token_Cnt[1]	LFSR[3] ⊕ Token_Cnt[3]	LFSR[2] ⊕ Token_Cnt[2]	LFSR[1] ⊕ Token_Cnt[1]
Token[1]	LFSR[3] ⊕ Token_Cnt[3]	LFSR[2] ⊕ Token_Cnt[2]	LFSR[3] ⊕ Token_Cnt[3]	LFSR[3] ⊕ Token_Cnt[3]
Token[2]	LFSR[0] ⊕ Token_Cnt[0]	LFSR[1] ⊕ Token_Cnt[1]	LFSR[0] ⊕ Token_Cnt[0]	LFSR[0] ⊕ Token_Cnt[0]
Token[3]	LFSR[2] ⊕ Token_Cnt[2]	LFSR[0] ⊕ Token_Cnt[0]	LFSR[1] ⊕ Token_Cnt[1]	LFSR[2] ⊕ Token_Cnt[2]

Table 2. SWDT Q&A Token Value, Part B
Response	Token value written to SWDT.Token_FP [11:10]
Response	00	01	10	11
Ans[0]	Count[1] ⊕ Token[0] ⊕ Token[3]	Count[1] ⊕ Token[0] ⊕ Token[1]	Count[1] ⊕ Token[1] ⊕ Token[2]	Count[1] ⊕ Token[2] ⊕ Token[3]
Ans[1]	Count[1] ⊕ Token[0] ⊕ Token[1] ⊕ Token[2]	Count[1] ⊕ Token[0] ⊕ Token[1] ⊕ Token[1]	Count[1] ⊕ Token[2] ⊕ Token[1] ⊕ Token[1]	Count[1] ⊕ Token[1] ⊕ Token[3] ⊕ Token[3]
Ans[2]	Count[1] ⊕ Token[0] ⊕ Token[1] ⊕ Token[3]	Count[1] ⊕ Token[0] ⊕ Token[1] ⊕ Token[1]	Count[1] ⊕ Token[2] ⊕ Token[1] ⊕ Token[1]	Count[1] ⊕ Token[1] ⊕ Token[2] ⊕ Token[3]
Ans[3]	Count[1] ⊕ Token[0] ⊕ Token[2] ⊕ Token[3]	Count[1] ⊕ Token[0] ⊕ Token[1] ⊕ Token[3]	Count[1] ⊕ Token[1] ⊕ Token[2] ⊕ Token[3]	Count[1] ⊕ Token[3] ⊕ Token[3] ⊕ Token[3]
Ans[4]	Count[0] ⊕ Token[1]	Count[0] ⊕ Token[0]	Count[0] ⊕ Token[2]	Count[0] ⊕ Token[3]
Ans[5]	Count[0] ⊕ Token[3]	Count[0] ⊕ Token[0]	Count[0] ⊕ Token[1]	Count[0] ⊕ Token[2]
Ans[6]	Count[0] ⊕ Token[0]	Count[0] ⊕ Token[1]	Count[0] ⊕ Token[2]	Count[0] ⊕ Token[3]
Ans[7]	Count[0] ⊕ Token[2]	Count[0] ⊕ Token[0]	Count[0] ⊕ Token[1]	Count[0] ⊕ Token[2]

Q&A Token Response Bits Table - AM011

Versal Adaptive SoC Technical Reference Manual (AM011)