High code coverage does not imply higj functional coverage?

stanlly9

這個論壇似乎沒有 Verification 的Topics
0 D' g( ]' c7 G9 j& Z我想請教的是：
/ \1 s! Z: w8 Y4 f! ~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

請問有人可以舉例嗎?
4 _8 O! F7 c! j! i7 @2 p什麼例子下
: @/ Z0 H% {" Q9 {% a+ `8 k& `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
Coverage 有六大類:

; {/ ~4 [) |9 j  X% _Line Coverage
; H6 M8 b. D3 ^' a6 S1 x% FConditional Coverage
FSM Coverage
Toggle Coverage
Branch Coverage
. b7 Z( U* G# f: K2 EPath Coverage
: x% g& `" F+ Z$ _( j- a1 e
有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,

6 `& g+ h" M' g$ ]9 }2 aalways @(posedge clk)
begin
      if(A)
% U, g, \- B; b$ R) Z Q <= #1 D0;
0 n7 y5 c3 I' l, F8 R! v2 p      else if(B)
Q <= #1 D1;
; B8 n3 e! F3 Uend
$ a( j$ l  V. m! H7 o4 n0 O0 w
, |7 f* \; f' e7 _//======================================//
1 v* g) p- M+ w
always @(posedge)
Q <= #1 (A)? D0 : (B)? D1 : Q;

$ n" n* s4 m& Y1 S* ]7 JThe 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,
4 P3 l+ O% j  c( W) k( BJarod

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.
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%.