High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
我想請教的是：
% R! d7 e: `# K% ?& u  hHigh 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
$ q. u! Q3 X, ?; B
' L; v  v5 Y# U請問有人可以舉例嗎?
% [- T& r& v  T1 W什麼例子下
會有 high code coverage 但是 functional coverage 卻不高
: E) n* h  O( J; z! s6 h( M[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:
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Line Coverage
. z& l. @' B; ~5 E8 m' fConditional Coverage
FSM Coverage
% l9 J" m- e% \% U6 O( ?4 Z( [Toggle Coverage
3 P( {! g: Q( xBranch Coverage
Path Coverage

有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,
! \, V+ [! \# m0 Z* ^" i1 l
  L0 S+ l) G' z, R% Talways @(posedge clk)
; U; ~- F/ i  ]9 @4 y9 @begin
      if(A)
/ j. z6 Y8 z2 f! }$ v9 X Q <= #1 D0;
5 |) |  C4 Q( [5 Q; E8 ]: g      else if(B)
Q <= #1 D1;
2 x7 [+ p* y0 O" Y; Hend

//======================================//

always @(posedge)
Q <= #1 (A)? D0 : (B)? D1 : Q;
6 B6 Z% R% g8 S& U: `
7 D7 Y2 U' y; n5 L- fThe code coverage of second is higher than that of the first.
5 D$ A  f' O; X* g  E) C! n$ b3 q$ X  o8 sThe code coverage is affected by the coding style.
The more readably code may have a low code coverage.
# ~) M  x9 w8 C5 i" C3 _
" F- y& [+ x; J) F1 s# D) M# q- lSincrely,
Jarod

kevin

code coverage:看low level design block(state machine,branch,case...)有幾成已被
/ s0 T" o0 r/ E1 e, qrun過.不代表function皆work,且符合spec.
  }" ~0 V& \. r. Z! i& N3 M4 ]7 PFunctional Coverage: 看design 的 function spec 有幾成已被check過.
code coverage 與 Functional Coverage是互補的.
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%.