High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
# E/ Y' d% r9 o+ C我想請教的是：
2 u' ?8 \2 |7 i8 q1 LHigh code coverage雖然是dynamic verification的第一步驟
但是通常並不意味著 一定會有 high functional coverage
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請問有人可以舉例嗎?
什麼例子下
會有 high code coverage 但是 functional coverage 卻不高
[聽說 functional coverage的界定不是很明確...請以自己的想法回答即可

masonchung

一般而言
. I* W  f6 @3 k; o4 p) @' ]. A0 NCoverage 有六大類:
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1 |% I" n8 E  Y8 a5 a3 ^6 ILine Coverage
Conditional Coverage
FSM Coverage
7 ^3 j2 J& s7 G' n: d$ `) k* lToggle Coverage
Branch Coverage
Path Coverage
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有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,

- O. q+ e, x& {3 v/ e8 t' ealways @(posedge clk)
begin
& ?' b4 u* f1 J; h" G9 y      if(A)
Q <= #1 D0;
      else if(B)
Q <= #1 D1;
end

. @2 n; C8 u0 F- T$ o//======================================//

always @(posedge)
* |2 y7 _. s+ ~* } Q <= #1 (A)? D0 : (B)? D1 : Q;
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The code coverage of second is higher than that of the first.
; g  Q$ e0 q) m8 `: jThe code coverage is affected by the coding style.
The more readably code may have a low code coverage.

Sincrely,
6 }7 M, T! R  s2 IJarod

kevin

code coverage:看low level design block(state machine,branch,case...)有幾成已被
run過.不代表function皆work,且符合spec.
2 S: K6 d0 a: v5 ~Functional Coverage: 看design 的 function spec 有幾成已被check過.
& _/ s) j5 P0 D/ h" Q/ Ycode coverage 與 Functional Coverage是互補的.
做Functional Coverage 也要有 functional coverage model.(跟 ic spec.有關)
0 W. ?! T# z" Q+ {8 ]: w舉個例,一個state machine,輸出順序跟 ic spec相反,code coverage 100%, Functional Coverage 0%.