High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
% k3 C% ~9 z+ ?- @我想請教的是：
High 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
: P6 g( `% |! L7 n$ \( t會有 high code coverage 但是 functional coverage 卻不高
' J" g% h, v" d+ V[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
Coverage 有六大類:

8 v. L- N/ O: }Line Coverage
Conditional Coverage
& _2 t& M+ e: z  d# LFSM Coverage
" V) J6 W' e9 r' VToggle Coverage
+ D0 g+ ?9 X% l- ?, w7 h! i: P9 gBranch Coverage
& f8 c4 }+ k5 _9 n! IPath Coverage

有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,
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always @(posedge clk)
: Q( n) P. W6 ]- X% M% mbegin
( Z$ s0 W# Z4 T1 u! [  O      if(A)
Q <= #1 D0;
$ S  D+ k; v* a      else if(B)
9 w  R) B- V2 S$ ^. u* C! ~( p Q <= #1 D1;
end
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3 K0 `# A! c5 x//======================================//

$ _. ]: O2 p. E7 F0 halways @(posedge)
, H. Y) a; B$ R" O Q <= #1 (A)? D0 : (B)? D1 : Q;

1 X+ w- N! U  V% [The code coverage of second is higher than that of the first.
, p$ G8 j" ^6 q# P% j$ NThe code coverage is affected by the coding style.
7 P# y) e' P$ V) u# s1 \4 pThe more readably code may have a low code coverage.

/ B9 L6 e1 d. N5 w" C" C* q: M' TSincrely,
) H1 w  G& q: T) 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.
# S: G7 C2 J% {" gFunctional Coverage: 看design 的 function spec 有幾成已被check過.
code coverage 與 Functional Coverage是互補的.
& Y* W4 k9 \4 w# z* j做Functional Coverage 也要有 functional coverage model.(跟 ic spec.有關)
舉個例,一個state machine,輸出順序跟 ic spec相反,code coverage 100%, Functional Coverage 0%.