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：
4 M) m$ ^! T* ~. q" S! H! e1 wHigh code coverage雖然是dynamic verification的第一步驟
7 y# C9 r* w& d5 k/ O! j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?
什麼例子下
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:
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Line Coverage
Conditional Coverage
FSM Coverage
3 Y; M5 ~: N1 \+ g& l( M- {( XToggle Coverage
* C; g; H  A0 c$ Z# l) ZBranch Coverage
1 [: d; X2 f- s# a# z/ @Path Coverage

有誰能說明這幾種 Coverage 的定義呢?

jarodz

For example,
5 g& |1 v! P% X# y
always @(posedge clk)
, ~3 j: S0 }# ]+ D1 ]" \begin
      if(A)
Q <= #1 D0;
7 Q+ V/ v- Y) T& ^! p      else if(B)
2 Z6 v9 K4 Y4 P6 Q" m  d Q <= #1 D1;
end
) G& b: q4 A9 m4 Y; X0 a
//======================================//
8 l+ ?% x# n3 h6 y
always @(posedge)
5 h1 x% F# H5 K5 m( P2 Z" Y$ i Q <= #1 (A)? D0 : (B)? D1 : Q;
4 N3 Y- A4 f: D7 l5 T. _
The code coverage of second is higher than that of the first.
. d; n" \" Q8 bThe code coverage is affected by the coding style.
# F7 Z6 d: w$ \+ a$ I$ `% q, fThe more readably code may have a low code coverage.
) t: h: \" L! [4 X8 o
% c( o  z. m! H3 }: s" o# Y6 h8 ]Sincrely,
6 p7 j  u2 J! K! Q/ N9 }6 ~  ^. wJarod

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.
$ j: U8 c) a& [6 [' j9 U( V1 gcode 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%.