High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
- f) S2 R) @8 B# [5 q: u我想請教的是：
High code coverage雖然是dynamic verification的第一步驟
, l/ k  b# W3 o( Y2 o; }8 N; ^; _( m但是通常並不意味著 一定會有 high functional coverage
* }1 y2 j5 ?' R# a8 i
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
+ _: |9 ~( ^- E% P9 s3 K* z[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:
1 t9 k, w+ N. p+ E
' j8 w5 _7 N! p+ w) YLine Coverage
Conditional Coverage
FSM Coverage
Toggle Coverage
' G9 O* g2 i8 w) c) oBranch Coverage
Path Coverage

. ^: Z  v7 b' L% {  E有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,

always @(posedge clk)
4 t1 ~) _: }5 {% u3 Y1 jbegin
" }$ q0 z- E+ r. t. C1 F. f      if(A)
Q <= #1 D0;
      else if(B)
Q <= #1 D1;
4 U& z1 C3 ]& c! Kend
' g& U- w3 B8 [8 T3 _' A/ |
2 D7 H5 a5 p$ P5 M" A# F5 ^2 X2 G//======================================//

always @(posedge)
Q <= #1 (A)? D0 : (B)? D1 : Q;
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The code coverage of second is higher than that of the first.
7 q: n) o( h/ ~9 U9 c; K# hThe code coverage is affected by the coding style.
The more readably code may have a low code coverage.
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Sincrely,
' i0 A. X' W# V7 O1 dJarod

kevin

code coverage:看low level design block(state machine,branch,case...)有幾成已被
  L' f$ J5 s5 d. W0 u  x- ^- c4 v. srun過.不代表function皆work,且符合spec.
Functional 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)
1 J* ~" @  _3 z+ ?舉個例,一個state machine,輸出順序跟 ic spec相反,code coverage 100%, Functional Coverage 0%.