High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
& n: k  i4 P; Q  i- x我想請教的是：
7 p! R' a$ K- }! ~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
. [3 Q8 s, `5 N' |3 z: F: |
請問有人可以舉例嗎?
% W0 I# B, V1 L" \0 p, D( x什麼例子下
, A1 s' L- o) o. M# J2 ~* {  ]會有 high code coverage 但是 functional coverage 卻不高
1 U; [4 Q! t, k% Z2 Q1 R; F: W[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
. U8 [1 D5 J+ G% ~9 F: FCoverage 有六大類:

# J3 b3 T5 C6 b, e1 t2 L- @9 G7 \Line Coverage
Conditional Coverage
FSM Coverage
. x# n$ o% P% I, C, aToggle Coverage
/ k8 U1 R9 }" {4 r/ I0 y1 dBranch Coverage
+ d$ K: Q0 m6 NPath Coverage
3 u) Z( \% d& O: R" ^+ b
有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,
# M3 }% |8 c4 U; ]4 B
# ]/ o" V/ {( l1 m, ~always @(posedge clk)
5 U3 q! p; {2 ^begin
. J9 }0 d7 f8 [( \1 a2 X! r6 M      if(A)
Q <= #1 D0;
      else if(B)
Q <= #1 D1;
end
) G  Y4 t4 q* |8 O1 y
//======================================//

0 r: W6 @) T7 x% P- z" p/ e. o( U$ [always @(posedge)
* d! l  \8 w! h. b0 R& N Q <= #1 (A)? D0 : (B)? D1 : Q;

The code coverage of second is higher than that of the first.
The code coverage is affected by the coding style.
The more readably code may have a low code coverage.

Sincrely,
Jarod

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.
  ?% z0 U# B6 e$ v9 u, ?- C) YFunctional 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%.