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--- intro_example:inverter [2020/04/29 14:38]
rajit
+++ intro_example:inverter [2022/05/13 09:15] (current)
rajit
@@ Line 4: / Line 4: @@
 An inverter is a very simple process that has a one-bit digital input and one bit digital output. The following specifies a process that corresponds to one inverter.
-<code>
+<code act>
 defproc inverter (bool? i; bool! o)
 {
@@ Line 15: / Line 15: @@
 Let's start with the statements
-<code>
+<code act>
  i -> o-
 ~i -> o+
@@ Line 33: / Line 33: @@
 This is a combinational gate, which means either the pull-up or pull-down network is always conducting (alternatively, the OR of the Boolean expressions for the pull-up and pull-down is always true). In this case, the pull-up and pull-down networks are complements of each other, so you only need specify one. The ''=>'' arrow can be used so that one rule can be used to specify both the pull-up and pull-down network as follows:
-<code>
+<code act>
 defproc inverter (bool? i; bool! o)
 {
@@ Line 47: / Line 47: @@
 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>
+<code act>
 inverter inv;
 </code>
-What can we do with this ACT file? The simplest thing is to simulate the inverter using a production-rule simulator. We have provided ''prsim'' for production rule simulation.
+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 act>
+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.