From b32a9738598b740bba5dc2298b74af2e827b25e9 Mon Sep 17 00:00:00 2001
From: Yann Herklotz <git@yannherklotz.com>
Date: Tue, 13 Apr 2021 20:03:37 +0100
Subject: Add

---
 verilog.tex | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'verilog.tex')

diff --git a/verilog.tex b/verilog.tex
index 3cc435c..e16a524 100644
--- a/verilog.tex
+++ b/verilog.tex
@@ -8,7 +8,7 @@ The Verilog semantics we use is ported to Coq from a semantics written in HOL4 b
 This semantics is quite practical as it is restricted to a small subset of Verilog, which can nonetheless be used to model the hardware constructs required for HLS.  The main features that are excluded are continuous assignment and combinational \alwaysblock{}s; these are modelled in other semantics such as that by~\citet{meredith10_veril}. %however, these are not necessarily needed, but require more complicated event queues and execution model.
 
 The semantics of Verilog differs from regular programming languages, as it is used to describe hardware directly, which is inherently parallel, rather than an algorithm, which is usually sequential.  The main construct in Verilog is the \alwaysblock{}.
-A module can contain multiple \alwaysblock{}s, all of which run in parallel.  These \alwaysblock{}s further contain statements such as if-statements or assignments to variables.  We support only \emph{synchronous} logic, which means that the \alwaysblock{} is triggered on (and only on) the rising edge of a clock signal.
+A module can contain multiple \alwaysblock{}s, all of which run in parallel.  These \alwaysblock{}s further contain statements such as if-statements or assignments to variables.  We support only \emph{synchronous} logic, which means that the \alwaysblock{} is triggered on (and only on) the rising or falling edge of a clock signal.
 %\NR{We should mention that variables cannot be driven by multiple \alwaysblock{}s, since one might get confused with data races when relating to concurrent processes in software.} \JW{Given the recent discussion on Teams, it seems to me that we perhaps don't need to mention here what happens if a variable is driven multiple times per clock cycle, especially since Vericert isn't ever going to do that.}
 
 The semantics combines the big-step and small-step styles. The overall execution of the hardware is described using a small-step semantics, with one small step per clock cycle; this is appropriate because hardware is routinely designed to run for an unlimited number of clock cycles and the big-step style is ill-suited to describing infinite executions. Then, within each clock cycle, a big-step semantics is used to execute all the statements.
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cgit 

