Subject: RE: [sv-ac] revised errata, JH goup 1
From: Bassam Tabbara (bassam@novas.com)
Date: Wed Jan 21 2004 - 14:22:27 PST
Yes it is, thx John.
-Bassam.
> -----Original Message-----
> From: owner-sv-ac@server.eda.org
> [mailto:owner-sv-ac@server.eda.org] On Behalf Of John Havlicek
> Sent: Wednesday, January 21, 2004 11:44 AM
> To: sv-ac@server.eda.org
> Subject: [sv-ac] revised errata, JH goup 1
>
>
> All:
>
> Bassam makes a good point that we should give an
> example that shows "##0" is illegal for combining
> differently-clocked sequences. I revised the
> one erratum change item that involves the illegal
> examples so that it reads:
>
>
> 5. 17.11.1, p. 245. Change
>
> Differently-clocked or multiply-clocked sequence operands cannot
> be combined with any sequence operators other than the
> multi-clock concatenation operator ##. For example, the
> following is illegal:
>
> (@(posedge clk1) x ##1 y) intersect (@(posedge clk2) z[*1:$])
>
> to
>
> Differently-clocked or multiply-clocked sequence operands cannot
> be combined with any sequence operators other than ##1.
> For example, if clk1 and clk2 are not identical, then
> the following
> are all illegal:
>
> @(posedge clk1) s1 ##0 @(posedge clk2) s2
>
> @(posedge clk1) s1 ##2 @(posedge clk2) s2
>
> @(posedge clk1) s1 intersect @(posedge clk2) s2
>
>
> Bassam: Is this good enough?
>
> The full text of the revised errata appears below.
>
> Best regards,
>
> John H.
>
> ==============================================================
> ==================
>
> SVA 3.1A DRAFT 3 ERRATA, JH GROUP 1
>
> ==============================================================
> ==================
> Erratum JH1: Parsing Problem with Clock Flow
> ==============================================================
> ==================
>
> Discussion
> ----------
>
> Proposal 12 on Clock Flow makes optional the specification of
> the clock in places that it is redundant. Thus, it is not
> necessary to write a clock event after the multi-clock
> concatentation "##" if the clock does not change. This
> introduces a parsing problem in determining whether what
> follows "##" is the parameter "n" of a singly-clocked "##n"
> or an expression operand of a multiply-clocked "##". The
> difficulty is illustrated in in the following example:
>
> @(c) s ## 2 ## 3 ## 4 ## 5 ## 6
>
> vs.
>
> @(c) s ## 2 ## 3 ## 4 ## 5 ## 6 7
>
> The latter actually means
>
> @(c) s ##2 ##3 ##4 ##5 ##6 7
>
>
> The proposed solution is to use "##1" instead of the special
> symbol "##" for multi-clock concatenation. In the formal
> semantics, "##" already means the same thing as "##1". This
> solves the parsing problem because every "##" must be
> followed by a parameter. "##1" is the only concatenation
> operator allowed for joining differently clocked sequences.
>
> The BNF for multi_clock_sequence allows a general
> cycle_delay_range for combining two multiply-clocked
> sequences. The semantic restriction
> to "##1" is described in the LRM text.
>
>
> BNF Changes
> -----------
>
> 1. 17.6, Syntax Box 17-4. Change
>
> multi_clock_sequence ## multi_clock_sequence
>
> to
>
> multi_clock_sequence cycle_delay_range multi_clock_sequence
>
> 2. 17.11, Syntax Box 17-15. Change
>
> multi_clock_sequence ## multi_clock_sequence
>
> to
>
> multi_clock_sequence cycle_delay_range multi_clock_sequence
>
> 3. Annex A, p. 410. Change
>
> multi_clock_sequence ## multi_clock_sequence
>
> to
>
> multi_clock_sequence cycle_delay_range multi_clock_sequence
>
>
> LRM Text Changes
> ----------------
>
> 1. 17.11.1, p. 245. Change the first paragraph from
>
> Multiply-clocked sequences are built by concatenating
> singly-clocked subsequences using the multi-clock concatenation
> operator ##. This operator is non-overlapping and synchronizes
> between the ending clock tick of the left hand sequence and the
> strictly subsequent starting clock tick of the right hand
> sequence.
>
> to
>
> Multiply-clocked sequences are built by concatenating
> singly-clocked sequences using the single-delay concatenation
> operator ##1. This operator is non-overlapping and synchronizes
> between the clocks of the two sequences. The single delay
> indicated by ##1 is understood to be from the endpoint of the
> first sequence, which occurs at a tick of the first clock, to
> the nearest strictly subsequent tick of the second clock, where
> the second sequence begins.
>
> 2. 17.11.1, line 9, p. 245. Change
>
> the above sequence is equivalent to
>
> to
>
> the above sequence is equivalent to the singly-clocked sequence
>
>
> 3. 17.11.1, p. 245. Change
>
> When using the multi-clock concatenation operator ##, both
> operands are required to admit only non-empty matches.
>
> to
>
> When concatenating differently-clocked sequences, the maximal
> singly-clocked subsequences are required to admit only non-empty
> matches.
>
>
> 4. 17.11.1, p. 245. Change
>
> The restriction to operands that do not match the empty word
> when using ## ensures that any multiply-clocked sequence has
> well-defined starting and ending clocking events and
> well-defined clock changes.
>
> to
>
> The restriction that maximal singly-clocked subsequences not
> match the empty word ensures that any multiply-clocked sequence
> has well-defined starting and ending clocking events and
> well-defined clock changes.
>
> 5. 17.11.1, p. 245. Change
>
> Differently-clocked or multiply-clocked sequence operands cannot
> be combined with any sequence operators other than the
> multi-clock concatenation operator ##. For example, the
> following is illegal:
>
> (@(posedge clk1) x ##1 y) intersect (@(posedge clk2) z[*1:$])
>
> to
>
> Differently-clocked or multiply-clocked sequence operands cannot
> be combined with any sequence operators other than ##1.
> For example, if clk1 and clk2 are not identical, then
> the following
> are all illegal:
>
> @(posedge clk1) s1 ##0 @(posedge clk2) s2
>
> @(posedge clk1) s1 ##2 @(posedge clk2) s2
>
> @(posedge clk1) s1 intersect @(posedge clk2) s2
>
>
> 6. 17.11.1, p. 245. Change all remaining instances of "##" to "##1"
> (but do not change "##1" to "##11"). [7 instances]
> [Note: There are 11 instances of "##" in this section in Draft 3,
> but 4 of these should be eliminated by the preceding changes.]
>
> 7. 17.11.2, p. 246. Examples on p. 246, change "##" to "##1"
> (but do not change "##1" to "##11"). [3 instance]
>
>
> 8. 17.11.3, p. 247. Examples on p. 247, change "##" to "##1"
> (but do not change "##1" to "##11"). [8 instances]
>
>
> 9. 17.11.3, p. 248. Examples on p. 248, change "##" to "##1"
> (but do not change "##1" to "##11"). [10 instances]
>
>
> Formal Semantics Changes
> ------------------------
>
> 1. H.2.1, p. 484. In the abstract grammar for clocked
> sequences, change "##"
> to "##1".
>
> 2. H.2.3.1, second bullet, p. 485. Change "##" to "##1".
>
> 3. H.3.1, p. 487. Delete the bullet "(S_1 ## S_2) |---> (S_1
> ##1 S_2)".
>
>
>
> ==============================================================
> ==================
> Erratum JH2: Clocked sequence parenthesis form missing in
> formal semantics
> ==============================================================
> ==================
>
> Discussion
> ----------
>
> By oversight, the BNF change allowing parentheses to be used
> on multiply-clocked sequences was not paralleled in the
> formal semantics.
>
> Formal Semantics Changes
> ------------------------
>
> 1. H.2.1, p. 484. Add a production to the abstract grammar
> for clocked
> sequences. Change
>
> S ::= @(b) R // "clock" form
> | ( S ## S ) // "concatenation" form
>
> to
>
> S ::= @(b) R // "clock" form
> | ( S ) // "parenthesis" form
> | ( S ##1 S ) // "concatenation" form
>
This archive was generated by hypermail 2b28 : Wed Jan 21 2004 - 14:30:24 PST