fault-secure parity prediction arithmetic operators michael nicolaidis ricardo o. duarte tima...
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Fault-Secure Parity Prediction Arithmetic Operators
MICHAEL NICOLAIDISRICARDO O. DUARTE
TIMA Laboratory
SALVADOR MANICHJOAN FIGUERAS
Polytechnic University of Catalonia
Outline
What is the problem ? Efficient Self-Checking Arithimetic Analysis of fault secureness Single-cell fan-out networks Take some examples Multiple-cell fan-out networks Implementations and experiments Conclusions
What’s The Problem ?
DRAWBACK: Parity prediction may not achieve fault- securene
ss , because single faults propagate o- -utput errors of random multiplicity.
Arithmetic codes can ensure falut secureness for most arithmetic operators.
Problem 1.Arithmetic code checkers are complex circuit 2.Arithmetic code are not compatible with p
arity checking 3.Must implement whole system with A~ code
Efficient self-checking arithimetic
Parity prediction schemes carries a lower overhead and a lower performance penalty than arithmetic coding schemes for small and medium-size operands.
And we are interest in efficient parity prediction implementations.
Method : Include arithemetic operators
Analysis of fault secureness
Definition: In a self-checking design, a circuit is fault secure if its output code detects all errors generated by each modeled fault.
Restriction: Cannot achieve fault secureness because even-multiplicity errors escape detection by parity code.
-Solution : 1.先分析 parity prediction cellular arithmetic operators來看不符合的原因 .
2.一一排解 .
continuous
Analysis of fault secureness
Basic components of cellular arithmetic operators : full- and half- adder cells.
5大主題 : Lemma1. 將不符合 fault-secure的 parity predictor電路給它獨立出來 .
Lemma2. 在不符合 fault-secure的 parity predictor電路中 ,將經由運算得到的 carries,拿來推算其可能產生的parity.
continuous
Analysis of fault secureness
Lemma3. 証明如果上圖的 sum(S)和 carry(C)使用同一個電路則 arithmetic operator將無法 fault secure.
continuous
Analysis of fault secureness
Lemma4. 証明如果一個 cell的 inputs只能生成 sum,carry,跟 redundant carry任兩個 ,則 operator也無法 fault secure.
continuous
Analysis of fault secureness
Lemma5. 証明如果說 C,Cp和 S在 logic有 fault而產生error給 C跟 Cp,則儘管 error會傳給下一個 S,但其仍可符合 fault secureness
Single-cell fan-out networks
Definition: any network in which each cell output enters exactly one input of exactly one cell is a single-cell fan-out networks.
Theorem1 : Parity prediction in a single-cell fan-out network using full- and half- adder cell designed as in Fig.3 achieves fault secureness.
continuous
Multiple-cell fan-out networks
A more complex implementation is required if some signals enter an even number of cell inputs.
Fig.9b is one solution. Fig.9c is another
solution with a double-rail checker.
Divider points
Each carry signal enters the row’s rightmost cell twice.
The divider generates two independent sets of outputs(remainder and quotient).
The leftmost cell’s carry and sum outputs have opposite values,and either can provide the quotient outputs.
The parity of sum outputs is PS=PCp+PN+PD+1 for even number of rows,it becomes PS=PCp+PN+1.