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--- intro_example:inverter [2020/04/29 14:34]
rajit
+++ intro_example:inverter [2020/12/02 01:00]
127.0.0.1 external edit
@@ Line 42: / Line 42: @@
 </code>
-Finally, the ''prs { ... }'' specifies the production rule body for the process. There are other bodies that can also be included, and they use different keywords instead of ''prs'' but the same basic structure.
+The ''prs { ... }'' specifies the production rule body for the process. There are other bodies that can also be included, and they use different keywords instead of ''prs'' but the same basic structure.
+The entire process is wrapped in the process definition. ''defproc'' is used to define a process. Here, we name the process ''inverter''. The signals ''i'' and ''o'' are in the //port list// for the process, which means they can be accessed from outside the process. They are declared as ''bool''s (Booleans), and the ''?'' means that ''i'' is an input, and the ''!'' means that ''o'' is an output.
+This fragment of ACT simply defines a process named ''inverter''. To actually create an inverter, we have to instantiate the process. The ''defproc'' can be viewed as defining the inverter type. We can use ''inverter'' just like we used ''bool'', and create an inverter called ''inv'' using the following:
+<code>
+inverter inv;
+</code>
+Next, we can simulate the inverter using a production-rule simulator. We have provided ''[[tools:prsim|prsim]]'' for production rule simulation as part of the ACT tools.
+===== Simulating with prsim =====
+The complete example is:
+<code>
+defproc inverter (bool? i; bool! o)
+{
+  prs {
+    i => o-
+  }
+}
+inverter inv;
+</code>
+If the file above is called ''test_inv.act'', a production rule file can be created from the ACT file by:
+<code>
+% aflat test_inv.act > test_inv.prs
+</code>
+The output file is the following:
+<code>
+"inv.i"->"inv.out"-
+~"inv.i"->"inv.out"+
+</code>
+Note that ACT uses ''.'' (like standard programming languages) as a separator between the name of the instance and internal nodes within it. (Note that magic, irsim use ''/'' as a separator; Xyce uses colon).
+If the file is saved as ''test_inv.prs'', it can be simulated using the production rule simulator called ''[[tools:prsim|prsim]]''.
+<code>
+% prsim test_inv.prs
+(Prsim) initialize
+(Prsim) watch inv.i
+(Prsim) watch inv.o
+(Prsim) status X
+(Prsim) set inv.i 0
+(Prsim) cycle
+(Prsim) set inv.i 1
+(Prsim) cycle
+</code>
+''prsim'' will check if the production rules being run are stable (i.e. hazard/glitch-free) and non-interfering (i.e. that pull-up and pull-down networks are not on simultaneously). It doesn't check all possible delay configurations, but just reports errors if it observes unstable or interfering production rules while the simulation is running. Try ''help'' as a ''prsim'' command to see the range of commands supported by ''prsim.''
+One of the useful features of ''prsim'' is that it can automatically randomize the delays of production rule firings. To do this, use
+<code>
+(Prsim) random
+</code>
+After this command, all delays are randomized. This is a useful test to see if your production rules are stable and non-interfering. If ''prsim'' finds that a production rule is unstable, it sets its output to ''X'' (for undefined). These ''X''s can propagate through the circuit.