Before using prsim to simulate a set of production rules, they must first be flattened using aflat. Assuming your production rules are in a file called circuit.act, you would run:
aflat circuit.act > circuit.prs prsim circuit.prs
This will give you an interactive (Prsim) prompt. Type help to get a list of simulation commands.
When running prsim, it is good practice to use a test .act file that looks something like this:
import "circuit.act";
...
... // your test setup
bool Reset;
prs {
Reset -> Vdd+
Reset -> GND-
Reset => _Reset-
}
In this example, I've assumed that the circuit reset signals are the global variables Reset and _Reset, and that both Vdd and GND are defined as globals for the power supplies. You should use the appropriate signals for your circuit there. The nice thing about this setup is that you can have a prsim script file that looks something like this:
random set Reset 1 cycle status U ... // watch various things set Reset 0 cycle
help
display a list of commands with short descriptions
exit
terminate
source <file>
read in a script file and execute the commands within
random [<min> <max>]
Set the random timing mode and optionally specify the default random timing bounds for all nodes.
random_seed <seed>
set the seed for the random timing mode.
norandom
Set the deterministic timing mode.
random_excl on|off
turn on/off random exclhi/lo firings
after <n> <minu> <maxu> <mind> <maxd>
For the random timing mode, set the random timing bounds for the up and down transitions for a specified node.
mode reset|run
set current running mode.
| Mode | Effect |
|---|---|
reset | reset turns off weak interference warnings (node still becomes X). During chip initialization, there can be weak interference since the simulator assumes all nodes are initially X. Setting the mode to reset during the reset phase prevents these warnings from being printed to the screen. |
run | Warnings of weak interference are enabled. This should be the standard mode after the reset phase has completed. |
initialize
initialize the simulation, setting all nodes to X.
step [<steps>]
simulate <steps> transitions (default is 1)
advance [<duration>]
simulate for <duration> units of simulation time (default is 1)
cycle [<node>]
simulate until the next transition on <node> (default is forever)
break <node>
set a breakpoint on <node>
break-on-warn
toggles the break-on-warn flag which stops/doesn't stop simulation on instability or interference
exit-on-warn
like break-on-warn, but exits prsim
set <variable> <value>
set the node, bus, or vector <variable> to specified <value>
get <variable>
get value of a node, bus, or vector <variable>
assert <variable> <value>
assert that the node, bus, or vector <variable> is <value>
uget <n>
get value of node <n> but report its canonical name
set_principal <n>
select <n> as the canonical name for a node
watch <n>
add watchpoint for <n>
unwatch <n>
delete watchpoint for <n>
watchall
watch all nodes
status 0|1|X [[^]str]
list all nodes with specified value, optional prefix/string match
pending
print the prsim pending event queue
alias <node>
list all of the name aliases for <node>
fanin <node>
print the production rules that drive <node>
fanin-get <node>
print the production rules that drive <node> with the values of each expression and node in the guards evaluated.
fanout <node>
print the set of nodes for which <node> appears in the guard of a driving production rule
chk-save <file>
save a simulation checkpoint to <file>
chk-restore <file>
restore simulation state from a checkpoint
dumptc <file>
dump transition counts for nodes to <file>
pairtc
turns on <input/output> pair transition counts
trace <file> <time>
Create atrace file for <time> duration
timescale <t>
set time scale to <t> picoseconds for tracing
Attributes can be added to production rules specified in ACT as follows:
prs {
[after=20] a & b #> c-
}
Attributes currently recognized by prsim are:
| Attribute | Meaning |
|---|---|
| after | used to set the delay in simulation time units for the production rule firing in non-random timing mode |
| weak | if there is a weak attribute, it means the production rule has a weak drive and can be overridden by a stronger production rule during simulation |
| unstab | if there is an unstab attribute, it means that the production rule may be unstable. prsim will suppress instability reporting on such rules |
The output of aflat can be very large, and designs with millions of gates can easily generate multi-gigabyte output files. To reduce the file size, the prspack command compresses the output of aflat by taking all the signal names in the production rule file ASCII output and converting them into an integer, saving all the names in the file on disk in a separate names file. To use this, say:
aflat circuit.act | prspack table > circuit.packprs
This creates a packed production rule file, as well as a number of files called table_idx.dat, table_str.dat, table_alias.dat, and table_rev.dat. These files are used to store alias information, strings, and hash tables to make it easy to access the names in the packed production rule output. These files can be used by prsim as follows:
prsim -n table circuit.packprs
The -n command line argument specifies where prsim can find all the signal names from the production rule file.