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IRSIM Users's Manual
NAME
irsim - An event-driven logic-level simulator for MOS circuits
SYNOPSIS
irsim [-s] prm file sim file ... [+hist file] [-cmd file ...]
- -------- -------- --------- --------
DESCRIPTION
IRSIM is an event-driven logic-level simulator for MOS (both N and P)
transistor circuits. Two simulation models are available:
switch
Each transistor is modeled as a voltage-controlled switch. Useful
for initializing or determining the functionality of the network.
linear
Each transistor is modeled as a resistor in series with a voltage-
controlled switch; each node has a capacitance. Node values and
transition times are computed from the resulting RC network, using
Chorng-Yeoung Chu's model. Chris Terman's original model is not
supported any more.
If the -s switch is specified, 2 or more transistors of the same type
connected in series, with no other connections to their common
source/drain will be stacked into a compound transistor with multiple
-------
gates.
The prm file is the electrical parameters file that configure the dev-
-
ices to be simulated. It defines the capacitance of the various layers,
transistor resistances, threshold voltages, etc... (see presim(1)).
If prm file does not specify an absolute path then IRSIM will search for
--------
the prm file as follows (in that order):
--------
1) ./<prm file> (in the current directory).
--------
2) ${CAD_ROOT}/irsim/prm/<prm file>
--------
3) ${CAD_ROOT}/irsim/prm/<prm file>.prm
--------
The default search directory (/usr/local/lib) can be overriden by setting
the environment variable CAD_ROOT to the appropriate directory prior to run-
ning IRSIM (i.e. setenv CAD_ROOT /usr/beta/mycad).
IRSIM first processes the files named on the command line, then (assum-
ing the exit command has not been processed) accepts commands from the
user, executing each command before reading the next.
File names NOT beginning with a '-' are assumed to be sim files (see
sim(5)), note that this version does not require to run the sim files
through presim. These files are read and added to the network database.
There is only a single name space for nodes, so references to node "A"
in different network files all refer to the same node. While this
feature allows one to modularize a large circuit into several network
files, care must be taken to ensure that no unwanted node merges happen
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due to an unfortunate clash in names.
File names prefaced with a '-' are assumed to be command files: text
files which contain command lines to be processed in the normal fashion.
These files are processed line by line; when an end-of-file is encoun-
tered, processing continues with the next file. After all the command
files have been processed, and if an "exit" command has not terminated
the simulation run, IRSIM will accept further commands from the user,
prompting for each one like so:
irsim>
The hist file is the name of a file created with the dumph command (see
- -----
below). If it is present, IRSIM will initilize the network to the state
saved in that file. This file is different from the ones created with
the ">" command since it saves the state of every node for all times,
including any pending events.
This version supports changes to the network through the update command.
Also, the capability to incrementally re-simulate the network up to the
current time is provided by the isim command.
COMMAND SUMMARY
@ filename take commands from command file
--------
? wnode... print info about node's source/drain connections
-----
! wnode... print info about node's gate connections
-----
< filename restore network state from file
--------
> filename write current network state to file
--------
<< filename same as "<" but restores inputs too
--------
| comment... comment line
-------
activity from [to] graph circuit activity in time interval
---- --
ana wnode... display nodes in analyzer window
-----
analyzer wnode... display nodes in analyzer window
-----
assert wnode [m] val assert that wnode equals value
----- - --- ----- -----
assertWhen nodeT valT node val
assert when a condition is met
back [time] move back to time
---- ----
c [n] simulate for n clock cycles (default:1)
- -
changes from [to] print nodes that changed in time interval
---- --
clock [node [val]] define value sequence for clock node
---- ---
clear clear analyzer window (remove signals)
d [wnode]... print display list or specified node(s)
-----
debug [debug level...]
-----------
set debug level (default: off)
decay [n] set charge decay time (0 => no decay)
-
display [arg]... control what gets displayed when
---
dumph filename... write net history to file
--------
hist [on|off] turn history on or off
exit [status] return to system
------
flush [time] flush out history up to time (default: now)
---- ----
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IRSIM Users's Manual
h wnode... make node logic high (1) input
-----
has coords print YES if transistor coordinates are available
-
inputs print current list of input nodes
ires [n] set incremental resolution to n ns
- -
isim [filename] incrementally resimulate changes form filename
-------- --------
l wnode... make node logic low (0) input
-----
logfile [filename] start/stop log file
--------
model [name] set simulation model to name
---- ----
p step clock one simulation step (phase)
path wnode... display critical path for last transition of a
-----
node
powlogfile [filename] start/stop power logfile
--------
powtrace -[node]... start/stop power tracing of specified
----
node(s)/vector(s)
powstep toggle the display of power estimate for each
timestep
print comment... print specified text
-------
printp print a list of all pending events
printx print all undefined (X) nodes
q terminate input from current stream
R [n] simulate for n cycles (default:longest sequence)
- -
readh filename read history from filename
-------- --------
report[level] set/reset reporting of decay events
-----
s [n] simulate for n ns. (default: stepsize)
- -
stepsize [n] set simulation step size to n ns.
- -
set vector value assign value to vector
------ ----- ----- ------
setlog[file|off] log net changes to file (off -> no log)
---- --- ---
setpath set search path for cmd files
stats print event statistics
sumcap print out the sum of the capacitance of all nodes
t [-]wnode... start/stop tracing of specified nodes
-----
tcap print list of shorted transistors
time [command] print resource utilization summary
-------
until wnode [mask] value count
delayed assert based on the clock count.
u wnode... make node undefined (X) input
-----
unitdelay [n] force transitions to take n ns. (0 disables)
- -
update filename read net changes from file
--------
V [node [value...]] define sequence of inputs for a node
---- -----
vector label node... define bit vector
----- ----
vsupply voltage set supply voltage for calculating power (default
-------
5V)
w [-]wnode... add/delete nodes from display list
-----
wnet [filename] write network to file
--------
x wnode... remove node from input lists
-----
Xdisplay [host:n] set/show X display (for analyzer)
---- -
COMMAND DESCRIPTIONS
Commands have the following simple syntax:
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cmd arg1 arg2 ... argn <newline>
---- ---- ----
where cmd specifies the command to be performed and the argi are argu-
----
ments to that command. The arguments are separated by spaces (or tabs)
and the command is terminated by a <newline>.
If cmd is not one of the built-in commands documented below, IRSIM
appends ".cmd" to the command name and tries to open that file as a com-
mand file (see "@" command). Thus the command "foo" has the same effect
as "@ foo.cmd".
Notation:
... indicates zero or more repetitions
[ ] enclosed arguments are optional
node name of node or vector in network
wnode
name of node or vector in network, can include '*' wildcard which
matches any sequence of zero or more characters. The pair of char-
acters '{' and '}' denote iteration over the limits enclosed by it,
for example: name{1:10} will expand into name1, name2 ... name10. A
----- ----- ------
3rd optional argument sets the stride, for example: name{1:10:2}
will expand into name1, name3, ... name7, name9.
----- ----- ----- -----
| comment...
Lines beginning with vertical bar are treated as comments and
ignored -- useful for comments or temporarily disabling certain
commands in a command file.
Most commands take one or more node names as arguments. Whenever a node
name is acceptible in a command line, one can also use the name of a bit
vector. In this case, the command will be applied to each node of the
vector (the "t" and "d" treat vectors specially, see below).
vector label node...
----- ----
Define a bit vector named "label" which includes the specified
nodes. If you redefine a bit vector, any special attributes of the
old vector (e.g., being on the display or trace list) are lost.
Wild cards are not accepted in the list of node names since you
would have no control over the order in which matching nodes would
appear in the vector.
The simulator performs most commands silently. To find out what's hap-
pened you can use one of the following commands to examine the state of
the network and/or the simulator.
set vector value
------ -----
Assign value to vector. For example, the following sequence of com-
----- ------
mands:
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vector BUS bit.1 bit.2 bit.3
set BUS 01x
The first command will define BUS to be a vector composed of nodes
---
bit.1, bit.2, and bit.3. The second command will assign the follow-
--- - --- - --- -
ing values:
bit.1 = 0
bit.2 = 1
bit.3 = X
Value can be any sequence of [0,1,h,H,l,L,x,X], and must be of the
same length as the bit vector itself.
d [wnode]...
-----
Display. Without arguments displays the values all nodes and bit
vectors currently on the display list (see w command). With argu-
ments, only displays the nodes or bit vectors specified. See also
the "display" command if you wish to have the display list printed
out automatically at the end of certain simulation commands.
w [-]wnode...
-----
Watch/unwatch one or more nodes. Whenever a "d" command is given,
each watched node will displayed like so:
node1=0 node2=X ...
To remove a node from the watched list, preface its name with a '-
'. If wnode is the name of a bit vector, the values of the nodes
-----
which make up the vector will be displayed as follows:
label=010100
where the first 0 is the value of first node in the list, the first
1 the value of the second node, etc.
assert wnode [mask] value
----- ---- -----
Assert that the boolean value of the node or vector wnode is value.
----- -----
If the comparison fails, an error message is printed. If mask is
----
given then only those bits corresponding to zero bits in mask take
----
part in the comparison, any character other than 0 will skip that
bit. The format of the error message is the following:
(tty, 3): assertion failed on 'name' 10X10 (1010X)
Where name is the name of the vector, followed by the actual value
----
and the expected value enclosed in parenthesis. If a mask is
----
specified, then bits that were not compared are printed as '-'.
until wnode [mask] value count
Acts just like the assert command except it requires an additional
argument <count> which is the max number of clock cycles to run.
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Instead of just testing the current state, like assert, until tests
for true and if false it runs clock cycles until condition becomes
true or count runs out.
ana wnode...
-----
This is a shorthand for the analyzer command (described below).
analyzer wnode...
-----
Add the specified node(s)/vector(s) to the analyzer display list
(see irsim-analyzer(3) for a detailed explanation). If the
analyzer window does not exist, it will be created. If no argu-
ments are given and the analyzer window already exists, nothing
happens.
Xdisplay [host:display]
---- -------
You must be able to connect to an X-server to start the analyzer.
If you haven't set up the DISPLAY environment variable properly,
the analyzer command may fail. If this is the case you can use the
Xdisplay command to set it from within the simulator. With no
arguments, the name of the current X-server will be printed.
clear
Removes all nodes and vectors from the analyzer window. This com-
mand is most useful in command scripts for switching between dif-
ferent signals being displayed on the analyzer.
"?" and "!" allow the user to go both backwards and forwards through the
network. This is a useful debugging aid.
? wnode...
-----
Prints a synopsis of the named nodes including their current values
and the state of all transistors that affect the value of these
nodes. This is the most common way of wandering through the net-
work in search of what went wrong.
The output from the command ? out looks like
---
out=0 (vl=0.3 vh=0.8) (0.100 pf) is computed from:
n-channel phi2=0 out=0 in=0 [1.0e+04, 1.3e+04, 8.7e+03]
pulled down by (a=1 b=1) [1.0e+04, 1.3e+04, 8.8e+03]
pulled up [4.0e+04, 7.4e+04, 4.0e+04]
The first line gives the node's name and current value, its low and
high logic thresholds, user-specifed low-to-high and high-to-low
propagation delays if present, and its capacitance if nonzero.
Succeeding lines list the transistor whose sources or drains con-
nect to this node: the transistor type ("pulled down" is an n-
channel transistor connected to gnd, "pulled up" is a depletion
pullup or p-channel transistor connected to vdd), the values of the
gate, source, and drain nodes, and the modeling resistances. Sim-
ple chains of transistors with the same implant type are collapsed
by the -s option into a single transistor with a "compound" gate;
-
compound gates appear as a parenthesized list of nodes (e.g., the
pulldown shown above). The three resistance values -- static,
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dynamic high, dynamic low -- are given in Kilo-ohms.
Finally, any pending events for a node are listed after the electr-
ical information.
! wnode...
-----
For each node in the argument list, print a list of transistors
controlled by that node.
tcap
Prints a list of all transistors with their source/drain shorted
together or whose source/drain are connected to the power supplies.
These transistors will have no effect on the simulation other than
their gate capacitance load. Although transistors connected across
the power supplies are real design errors, the simulator does not
complain about them.
Any node can be made an input -- the simulator will not change an input
node's value until it is released. Usually on specific nodes -- inputs
to the circuit -- are manipulated using the commands below, but you can
fool with a subcircuit by forcing values on internal nodes just as
easily.
h wnode...
-----
Force each node on the argument list to be a high (1) input. Over-
rides previous input commands if necessary.
l wnode...
-----
Like "h" except forces nodes to be a low (0) input.
u wnode...
-----
Like "h" except forces nodes to be a undefined (X) input.
x wnode...
-----
Removes nodes from whatever input list they happen to be on. The
next simulation step will determine the correct node value from the
surrounding circuit. This is the default state of most nodes.
Note that this does not force nodes to have an "X" value -- it sim-
ply removes them from the input lists.
inputs
prints the high, low, and undefined input lists.
It is possible to define a sequence of values for a node, and then cycle
the circuit as many times as necessary to input each value and simulate
the network. A similar mechanism is used to define the sequence of
values each clock node goes through during a single cycle.
Each value is a list of characters (with no intervening blanks) chosen
from the following:
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1, h, H logic high (1)
0, l, L logic low (0)
u, U undefined (X)
x, X remove node from input lists
Presumably the length of the character list is the same as the size of
the node/vector to which it will be assigned. Blanks (spaces and tabs)
are used to separate values in a sequence. The sequence is used one
value at a time, left to right. If more values are needed than supplied
by the sequence, IRSIM just restarts the sequence again.
V [node [value...]]
---- -----
Define a vector of inputs for a node. After each cycle of an "R"
command, the node is set to the next value specified in the
sequence.
With no arguments, clears all input sequences (does not affect
clock sequences however). With one argument, "node", clears any
input sequences for that node/vector.
clock [node [value...]]
---- -----
Define a phase of the clock. Each cycle, each node specified by a
clock command must run through its respective values. For example,
clock phi1 1 0 0 0
clock phi2 0 0 1 0
defines a simple 4-phase clock using nodes phi1 and phi2. Alterna-
---- ----
tively one could have issued the following commands:
vector clk phi1 phi2
clock clk 10 00 01 00
With no arguments, clears all clock sequences. With one argument,
"node", clears any clock sequences for that node/vector.
After input values have been established, their effect can be propagated
through the network with the following commands. The basic simulated
time unit is 0.1ns; all event times are quantized into basic time units.
A simulation step continues until stepsize ns. have elapsed, and any
--------
events scheduled for that interval are processed. It is possible to
build circuits which oscillate -- if the period of oscillation is zero,
the simulation command will not return. If this seems to be the case,
you can hit <ctrl-C> to return to the command interpreter. Note that if
you do this while input is being taken from a file, the simulator will
bring you to the top level interpreter, aborting all pending input from
any command files.
When using the linear model (see the "model" command) transition times
are estimated using an RC time constant calculated from the surrounding
circuit. When using the switch model, transitions are scheduled with
unit delay. These calculations can be overridden for a node by setting
its tplh and tphl parameters which will then be used to determine the
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time for a transition.
s [n]
-
Simulation step. Propogates new values for the inputs through the
network, returns when n (default: stepsize) ns. have passed. If n
- -------- -
is specified, it will temporarily override the stepsize value.
--------
Unlike previous versions, this value is NOT remembered as the
default value for the stepsize parameter. If the display mode is
--------
"automatic", the current display list is printed out on the comple-
tion of this command (see "display" command).
c [n]
-
Cycle n times (default: 1) through the clock, as defined by the
-
"clock" command. Each phase of the clock lasts stepsize ns. If
--------
the display mode is "automatic", the current display list is
---------
printed out on the completion of this command (see "display" com-
mand).
p Step the clock through one phase (or simulation step). For exam-
ple, if the clock is defined as above
clock phi1 1 0 0 0
clock phi2 0 0 1 0
then "p" will set phi1 to 1 and phi2 to 0, and then propagate the
effects for one simulation step. The next time "p" is issued, phi1
and phi2 will both be set to 0, and the effects propagated, and so
on. If the "c" command is issued after "p" has been used, the
effect will be to step through the next 4 phases from where the "p"
command left off.
R [n]
-
Run the simulator through n cycles (see the "c" command). If n is
- -
not present make the run as long as the longest sequence. If
display mode is automatic (see "display" command) the display is
printed at the end of each cycle. Each "R" command starts over at
the beginning of the sequence defined for each node.
back time
----
Move back to the specified time. This command restores circuit
state as of time, effectively undoing any changes in between. Note
----
that you can not move past any previously flushed out history (see
flush command below) as the history mechanism is used to restore
the network state. This command can be useful to undo a mistake in
the input vectors or to re-simulate the circuit with a different
debug level.
path wnode...
-----
display critical path(s) for last transition of the specified
node(s). The critical path transistions are reported using the
following format:
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node -> value @ time (delta)
---- ----- ---- -----
where node is the name of the node, value is the value to which the
---- -----
node transitioned, time is the time at which the transistion
----
occurred, and delta is the delay through the node since the last
-----
transition. For example:
critical path for last transition of Hit v1:
-
phi1-> 1 @ 2900.0ns , node was an input
PC driver-> 0 @ 2900.4ns (0.4ns)
-
PC b q1-> 1 @ 2904.0ns (3.6ns)
- -
tagDone b v1-> 0 @ 2912.8ns (8.8ns)
- -
tagDone1 v1-> 1 @ 2915.3ns (2.5ns)
-
tagDone1 b v1-> 0 @ 2916.0ns (0.7ns)
- -
tagDone v1-> 1 @ 2918.4ns (2.4ns)
-
tagCmp b v1-> 0 @ 2922.1ns (3.7ns)
- -
tagCmp v1-> 1 @ 2923.0ns (0.9ns)
-
Vbit b v1-> 0 @ 2923.2ns (0.2ns)
- -
Hit v1-> 1 @ 2923.5ns (0.3ns)
-
activity from time [to time]
--------- -------
print histogram showing amount of circuit activity in the specified
time inteval. Actually only shows number of nodes which had their
most recent transition in the interval.
changes from time [to time]
--------- -------
print list of nodes which last changed value in the specified time
interval.
printp
print list of all pending events sorted in time. The node associ-
ated with each event and the scheduled time is printed.
printx
print a list of all nodes with undefined (X) values.
Using the trace command, it is possible to get more detail about what's
happening to a particular node. Much of what is said below is described
in much more detail in "Logic-level Simulation for VLSI Circuits" by
Chris Terman, available from Kluwer Academic Press. When a node is
traced, the simulator reports each change in the node's value:
[event #100] node out.1: 0 -> 1 @ 407.6ns
The event index is incremented for each event that is processed. The
transition is reported as
old value -> new value @ report time
--- ----- --- ----- ------ ----
Note that since the time the event is processed may differ from the
event's report time, the report time for successive events may not be
strictly increasing.
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Depending on the debug level (see the "debug" command) each calculation
of a traced node's value is reported:
[event #99] node clk: 0 -> 1 @ 400.2ns
final value( Load ) V=[0.00, 0.04] => 0
-
..compute tau( Load )
-
{Rmin=2.2K Rdom=2.2K Rmax=2.2K} {Ca=0.06 Cd=0.17}
tauA=0.1 tauD=0.4 ns
[event #99: clk->1] transition for Load: 1 -> 0 (tau=0.5ns,
delay=0.6ns)
In this example, a calculation for node Load is reported. The calcula-
----
tion was caused by event 99 in which node clk went to 1. When using the
linear model (as in this example) the report shows
current value -> final value
------- ----- ----- -----
The second line displays information regarding the final value (or dc)
analysis for node "Load"; the minimun and maximum voltages as well as
the final logical value (0 in this case).
The next three lines display timing analysis information used to esti-
mate the delays. The meaning of the variables displayed can be found
Chu's thesis: "Improved Models for Switch-Level Simulation".
When the final value is reported as "D", the node is not connected to an
----- -----
input and may be scheduled to decay from its current value to X at some
later time (see the "decay" command).
-------
"tau" is the calculated transition time constant, "delta" is when any
consequences of the event will be computed; the difference in the two
times is how IRSIM accounts for the shape of the transition waveform on
subsequent stages (see reference given above for more details). The
middle lines of the report indicate the Thevenin and capacitance parame-
ters of the surrounding networks, i.e., the parameters on which the
transition calculations are based.
debug [ev dc tau taup tw spk][off][all]
-- -- --- ---- -- --- --- ---
Set debugging level. Useful for debugging simulator and/or circuit
at various levels of the computation. The meaning of the various
debug levels is as follows:
ev display event enqueueing and dequeueing.
dc display dc calculation information.
tau display time constant (timing) calculation.
taup display second time constant (timing) calculation.
tw display network parameters for each stage of the tree walk,
this applies to dc, tau, and taup. This level of debugging
detail is usually needed only when debugging the simulator.
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spk displays spike analysis information.
all This is a shorthand for specifying all of the above.
off This turns off all debugging information.
If a debug switch is on then during a simulation step, each time a
watched node is encounted in some event, that fact is indicated to
the user along with some event info. If a node keeps appearing in
this prinout, chances are that its value is oscillating. Vice
versa, if your circuit never settles (ie., it oscillates) , you can
use the "debug" and "t" commands to find the node(s) that are caus-
ing the problem.
Without any arguments, the debug command prints the current debug
level.
t [-]wnode...
-----
set trace flag for node. Enables the various printouts described
above. Prefacing the node name with '-' clear its trace flag. If
"wnode" is the name of a vector, whenever any node of that vector
changes value, the current time and the values of all traced vec-
tors is printed. This feature is useful for watching the relative
arrival times of values at nodes in an output vector.
System interface commands:
> filename
--------
Write current state of each node into specified file. Useful for
making a breakpoint in your simulation run. Only stores values so
isn't really useful to "dump" a run for later use, i.e., the
current input lists, pending events, etc. are NOT saved in the
state file.
< filename
--------
Read from specified file, reinitializing the value of each node as
directed. Note that network must already exist and be identical to
the network used to create the dump file with the ">" command.
These state saving commands are really provided so that complicated
initializing sequences need only be simulated once.
<< filename
--------
Same as "<" command, except that this command will restore the
input status of the nodes as well. It does not, however, restore
-----
pending events.
dumph [filename]
--------
Write the history of the simulation to the specified file, that is;
all transistions since time = 0. The resulting file is a machine-
independent binary file, and contains all the required information
to continue simulation at the time the dump takes place. If the
filename isn't specified, it will be constructed by taking the name
of the sim file (from the command line) and appending ".hist" to
-
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it.
readh filename
--------
Read the specified history-dump file into the current network.
This command will restore the state of the circuit to that of the
dump file, overwriting the current state.
flush [time]
----
If memory consumption due to history maintanance becomes prohibi-
tive, this command can be used to free the memory consumed by the
history up to the time specified. With no arguments, all history
up to the current point in the simulation is freed. Flushing out
the history may invalidate an incremental simulation and the por-
tions flushed will no longer appear in the analyzer window.
setpath [path...]
----
Set the search-path for command files. Path should be a sequence
----
of directories to be searched for ".cmd" files, "." meaning the
current directory. For eaxmple:
setpath . /usr/me/rsim/cmds /cad/lib/cmds
With no arguments, it will print the current search-path. Ini-
tially this is just ".".
print text...
----
Simply prints the text on the user's console. Useful for keeping
user posted of progress through a long command file.
logfile [filename]
--------
Create a logfile with the specified name, closing current log file
if any; if no argument, just close current logfile. All output
which appears on user's console will also be placed in the logfile.
Output to the logfile is cleverly formatted so that logfiles them-
selves can serve as command files.
setlog [filename | off]
-------- ---
Record all net changes, as well as resulting error messages, to the
specified file (see "update" command). Net changes are always
appended to the log-file, preceding each sequence of changes by the
current date. If the argument is off then net-changes will not be
---
logged. With no arguments, the name of the current log-file is
printed.
The default is to always record net changes; if no filename is
specified (using the "setlog" command) the default filename
irsim changes.log will be used. The log-files are formatted so
------------- ---
that log-files may themselves be used as net-change files.
wnet [filename]
--------
Write the current network to the specified file. If the filename
isn't specified, it will be constructed by taking the name of the
sim file (from the command line) and appending ".inet" to it. The
-
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resulting file can be used in a future simulation run, as if it
were a sim file. The file produced is a machine independent binary
file, which is typically about 1/3 the size of the sim file and
about 8 times faster to load.
time [command]
-------
With no argument, a summary of time used by the simulator is
printed. If arguments are given the specified command is timed and
a time summary is printed when the command completes. The format
of the time summary is Uu Ss E P% M, where:
- - - - -
U => User time in seconds
-
S => System time in seconds
-
E => Elapsed time, minutes:seconds
-
P => Percentage of CPU time (((U + S)/E) * 100)
-
M => Median text, data, and stack size use
-
q
Terminate current input stream. If this is typed at top level, the
simulator will exit back to the system; otherwise, input reverts to
the previous input stream.
exit [n]
-
Exit to system, n is the reported status (default: 0).
-
Simulator parameters are set with the following commands. With no argu-
ments, each of the commands simply prints the current value of the
parameter.
decay [n]
-
Set decay parameter to n ns. (default: 0). If non-zero, it tells
-
the number of ns. it takes for charge on a node to decay to X. A
value of 0 implies no decay at all. You cannot specify this param-
eters separately for each node, but this turns out not to be a
problem. See "report" command.
display [-][cmdfile][automatic]
------- ---------
set/reset the display modes, which are
cmdfile commands executed from command files are displayed to
user before executing. The default is cmdfile = OFF.
------- ---
automatic print out current display list (see "d" command) after
completion of "s" or "c" command. The default is
automatic = ON.
--------- --
Prefacing the previous commands with a "-" turns off that display
option.
model [name]
----
Set simulation model to one of the following:
switch
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Model transistors as voltage controlled switches. This model
uses interval logic levels, without accounting for transistor
resistances, so circuits with fighting transistors may not be
accuratelly modelled. Delays may not reflect the true speed of
----
the circuit as well.
linear
Model transistors as a resistor in series with a voltage con-
trolled switch. This model uses a single-time-constant computed
from the resulting RC network and uses a two-time-constant model
to analyze charge sharing and spikes.
The default is the linear model. You can change the simulation
model at any time -- even with events pending -- as only new calcu-
lations are affected. Without arguments, this command prints the
current model name.
report [level]
-----
When level is nonzero, report all nodes which are set to X because
of charge decay, regardless on whether they are being traced. Set-
ting level to zero disables reporting, but not the decay itself
(see "decay" command).
stepsize [n]
-
Specify duration of simulation step or clock phase. n is specified
- -- ---------
in ns. (nanoseconds). Floating point numbers with up to 1 digit
past the decimal point are allowed. Further decimals are trucated
(i.e. 10.299 == 10.2).
unitdelay [n]
-
When nonzero, force all transitions to take n ns. Setting the
-
parameter to zero disables this feature. The resolution is the
same as for the "stepsize" command.
stats
Print event statitistics, as follows:
changes = 26077
punts (cns) = 208 (34)
punts = 0.79%, cons punted = 16.35%
-
nevents = 28012; evaluations = 27972
Where changes is the total number of transistions recorded, punts
------- -----
is the number of punted events, (cns) is the number of consecutive
---
punted events (a punted event that punted another event). The
penultimate line shows the percentage of punted events with respect
to the total number of events, and the percentage of consecutive
punted events with respect to the number of punted events. The
last line shows the total number of events (nevents) and the number
of net evaluations.
Incremental simulation commands:
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Irsim supports incremental changes to the network and resimulation of
the resulting network. This is done incrementally so that only the
nodes affected by the changes, either directly or indirectly, are re-
evaluated.
update filename
--------
Read net-change tokens from the specified file. The following
net-change commands are available:
add type gate source drain length width [area]
delete type gate source drain length width [area]
move type gate source drain length width [area] g s d
cap node value
N node metal-area poly-area diff-area diff-perim
M node M2A M2P MA MP PA PP DA DP PDA PDP
thresh node low high
Delay node tplh tphl
For a detailed dscription of this file see netchange(5). Note that
this is an experimental interface and is likely to change in the
future.
Note that this command doesn't resimulate the circuit so that it
may leave the network in an inconsistent state. Usually this com-
mand will be followed by an isim command (see below), if that is
not the case then it's up to the user to initilize the state of the
circuit. This command exists only for historical reasons and will
probably disappear in the future. It's use is discouraged.
isim [filename]
--------
Read net-change tokens from the specified file (see netchange(5))
and incrementally resimulate the circuit up to the current simula-
tion time (not supported yet).
ires n
-
The incremental algorithm keeps track of nodes deviating from their
past behavior as recorded in the network history. During resimula-
tion, a node is considered to deviate from its history if it's new
state is found to be different within n ns of its previous state.
-
This command allows for changing the incremental resolution. With
no arguments, it will print the current resolution. The default
resolution is 0 ns.
powlogfile [filename]
--------
Opens filename for writting nodal transition reports. The format of
--------
the report is the same you get when you trace a node normaly. With
no arguments powlogfile just closes the opened logfile and prints
out a power dissipation summary. Nodal transitions in inputs are
not included in the transition count.
powtrace [[-]node...]
----
The syntax of this command is the same as the normal t (trace)
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command. If you want to trace and report power dissipation for all
the nodes just use powtrace *. Use powtrace -node if you want to
exclude some nodes.
powstep
Toggles whether dynamic power estimation is displayed after each
timestep. The ynamic power displayed will only be for the nodes
that have been selected using the powtrace command.
vsupply voltage
-------
Sets the V variable for use in the P=CV^2/(2t) expression where C
is capacitance switched, and t is the timestep. The default value
for vsupply is 5.0 Volts.
sumcap
Gives a sum of all nodal capcitances, not just those selected with
the powtrace command.
SEE ALSO
presim(1) (now obsolete)
rsim(1)
irsim-analyzer(3)
sim(5)
netchange(5)
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