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：
! d/ T/ o4 T' r- oHigh 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
! O6 C9 W4 z" U
) D. N0 w6 A1 H+ c+ a* H# s6 P請問有人可以舉例嗎?
6 M- t8 r5 N- R3 b什麼例子下
, ?- c4 p; [4 }- B5 o* z: p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
/ b1 ]1 H8 `: Y4 l6 D8 eCoverage 有六大類:

Line Coverage
" K/ p2 h7 i4 ^, RConditional Coverage
3 Q, K8 u- Q+ V1 G: ?FSM Coverage
Toggle Coverage
Branch Coverage
; V# c1 V! i3 }- bPath Coverage
2 s5 D5 b/ A; x3 z) g
  P$ X3 _# Y0 Q6 N有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,

always @(posedge clk)
begin
2 M! T# c" d* r5 E( I4 b      if(A)
2 U8 N, D; u' ? Q <= #1 D0;
9 k- K, v6 X! w+ L  d. n2 r$ w) ~' i      else if(B)
Q <= #1 D1;
end

2 N, x3 v$ u% A3 k' [//======================================//
" [! K* S$ J! W
always @(posedge)
! G8 ^6 `1 d. F! D6 N Q <= #1 (A)? D0 : (B)? D1 : Q;
$ ~$ S6 T8 X1 I1 y$ K
" e; d# W5 E- G* q2 j8 GThe code coverage of second is higher than that of the first.
4 M% s  R( B  P4 k4 M; ?) xThe code coverage is affected by the coding style.
, t" X0 o  e9 x' h! MThe more readably code may have a low code coverage.
, D& e" L2 x1 u% t
' k8 ?; Z/ h8 X/ R1 L- S9 |& mSincrely,
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.
Functional Coverage: 看design 的 function spec 有幾成已被check過.
5 k( y/ M- n( c4 d9 G& C+ `4 qcode 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%.