Other Simulation Features


   1.  If there are any circuit elements with unconnected pins, AnaLOG
       will refuse to simulate.  If you meant to leave the pin
       unconnected, you must connect it to something like a "dummy"
       capacitor to ground.  If there are unconnected gates, the
       NUMBERS icon will display a message of the form "OPAMP is
       unconnected".  Digital LOG doesn't mind unconnected pins on

   2.  If you give a ":DIM" command, AnaLOG gates will be drawn in dim
       colors until they are fully connected.  Another ":DIM" turns this
       mode off.  This command only works with the analog simulator.

   3.  Select Probe in the Cursor menu (or press the "." key) to enable
       Probe mode.  The cursor changes to a different style arrow; when
       you move this arrow over a gate or wire, a message below the
       AnaLOG NUMBERS icon shows the internal state of the gate and/or
       node.  In Digital LOG, the lines at the bottom of the screen light
       up according to the state of the node being probed.  Probe mode
       also displays the name of a gate being touched.  Select again
       to turn the mode off.  You can also press "e" or "x"
       ("Examine") for a temporary Probe mode which turns off
       automatically when you click the right button.

   4.  Select Glow in the Cursor menu (or press the "g" key) to enable
       Glow mode.  Wires "glow" in colors according to the voltages
       they carry.  In AnaLOG:

            Black       means at (or below) ground.
            Dark red    means within one transistor threshhold of ground.
            Red         means an intermediate voltage.
            Pink        means within one transistor threshhold of VDD.
            White       means at (or above) VDD.
            Green       means the wire is not driven by an analog gate.

       In digital LOG:

            Black       means the wire carries a Zero.
            Red         means the wire carries a One.
            Green       means the wire is not driven.

       Glow mode may be left on at all times, though it may make the
       simulation a little slower.

   5.  Select Simulation in the Misc menu (or press the "o" key)
       to turn the simulator off or back on again.  When simulation is
       off, the gates and nodes of the circuit appear to freeze at their
       last simulated values.  Turning the simulator back on resumes the

   6.  Press the "t" key to simulate for one time-step, then stop.
       You can press t as many time as you wish to see the simulation
       evolve, then press o to turn full-speed simulation back on.

   7.  LOG tries to balance simulation speed against response time for
       the mouse and keyboard.  If you let go of the mouse and don't press
       any keys, LOG slowly shifts the balance to prefer simulation.
       When you again use the mouse or keyboard the balance reverts to
       favoring editing.  You can press the "f" key to switch
       immediately to "fast" mode (preferring simulation over editing).


   1.  Numbers are great, but real people like to see plots of their
       output waveforms.  In LOG, the mechanism for this is called
       Scope mode.  To use it, first connect terminals (TO or FROM)
       to each signal to be monitored and give the signals unique
       names, then select SCOPE in the Misc menu, or press the "s"
       key.  The scope can display both digital and analog signals.

   2.  The Scope screen consists of a large field of dots representing
       the "divisions" on a normal scope face, an area to the left of
       the dots where signal names can go, and some menu words at the
       bottom.  Use the mouse as usual to select menu words for the
       functions that you want.  In particular, touch QUIT (there's
       one on each side, for your convenience!) or hit Control-C to
       return to the circuit diagram.

   3.  To display a certain signal on the scope, just type the name
       of the signal and press ENTER.  The name will appear somewhere
       at the left edge.  You can use the mouse to press and drag the
       name to any vertical location.  To remove a signal name, drag
       it off the top or bottom edge.

   4.  Initially, the scope is not "triggered," so nothing is
       displayed.  To begin taking data, touch Trigger.  The scope
       also automatically triggers when you reset the simulation; there
       is a handy Reset on the menu too.  A few moments after you
       trigger the scope, lines to the right of the signal names
       will begin to appear.

   5.  In all probability, the lines will be absurdly wide or
       ridiculously thin.  In other words, the time scale is wrong.
       To fix this, press the "<" or ">" keys to shrink or expand
       (respectively) the plot until it fits nicely on the screen.
       You can also use the arrow keys to scroll around the plots in time;
       by scrolling and expanding you can focus in on any part of the
       simulation history.

   6.  Touch Config to change the various Scope mode parameters.
       You will find here the seconds-per-division and seconds-at-
       left-edge parameters that the zoom and scroll commands
       manipulate graphically; you can set them numerically if you
       prefer.  The current time and timestep are displayed for
       your reference in setting these values.

   7.  Scope mode has a limit on the number of data points it will
       take before stopping, initially 2000.  You can set this in
       the Config screen, but beware that if you set it too high
       AnaLOG will run out of memory and lose ALL of your data!.
       This screen also displays the number of data points taken
       so far.  What happens when this reaches the maximum depends
       on the "trigger mode" attribute:

            Manual:        Scope starts taking data when you touch
                           "Trigger," and stops when you touch "Trigger"
                           again, or when all the data points are used.
                           Beware that when memory fills, there is no way
                           to resume taking data except by retriggering
                           and losing all of your old data!  LOG prints
                           warning messages when you are about to run
                           out of data points.

            On Reset:      Like Manual, but also triggers automatically
                           on RESET.  This is the default mode.

            Triggered:     Like Manual, but also triggers automatically
                           when a triggering pulse is detected on the
                           signal that you specify.  Not relevant for
                           AnaLOG, because triggering on analog signals
                           has not yet been implemented.

            Continuous:    Triggers manually or on RESET.  When data
                           memory is full, old data points are removed
                           from the left and new ones added to the
                           right.  Never stops triggering unless you
                           turn it off by hand.

       On Reset mode is typically used when you are interested in the
       first data points of a long simulation; Continuous mode is for
       when you are interested in the most recent data points.

       Note that the word "Trigger" is lit whenever the Scope is taking
       data, and unlit otherwise.

   8.  Normally, Scope mode records exactly one data point per timestep
       returned by the simulator.  The "minimum timestep" and "maximum
       timestep" attributes can modify this.  If you would like to
       conserve memory and take data points only at, say, 100us intervals,
       you could set "minimum timestep" to 100us.  Scope mode will then
       record a data point only if it's been at least 100us since the last
       point was taken.  The other attribute, "maximum timestep," does
       not work with the analog simulator.

   9.  When you touch (instead of dragging) a signal name on the left edge,
       you Configure the parameters for that signal's particular trace.  In
       AnaLOG, you can set volts-per-division, plus an "origin" voltage for
       plotting small signals (for example, if you have a signal that
       varies slightly around 2V, set the origin to 2V and the scale to,
       say, 50mV per division).  You can also change the color of the
       trace, very helpful for plotting several traces on top of one
       another.  You can also set logarithmic mode, in which case you
       specify "Vzero" which is the voltage to plot at the origin, with one
       decimal order of magnitude per division above and below.

  10.  To plot an AnaLOG current, you must take an ISCOPE gate, which is
       the funny-looking meter with a hook coming out the back, connect it
       to the pin to be measured, and connect a terminal (TO or FROM) to
       the "hook." Now, when you monitor that name in Scope mode, you will
       measure Amps instead of Volts.  Note that the "hook" pin of the
       ISCOPE is a special "current-mode" data type, and any attempt to
       connect it to a normal analog signal will fail.  If an ISCOPE ever
       appears to undergo spontaneous combustion, it is because you put it
       down with the hook touching an analog wire.

  11.  If you try pressing down the mouse anywhere in the grid of dots,
       you will get a horizontal and/or vertical line whose meaning
       depends on two indicators at the bottom of the screen:

            Absolute:      Display the value of time, or of the
                           currently-selected signal, that corresponds
                           to the mouse position.

            Delta:         Display the difference in time or signal
                           value that corresponds to the distance between
                           the current mouse position, and the position at
                           which it was first pressed down.

            Value:         Display the value of the current signal as
                           of the time that corresponds to the mouse
                           position.  For example, you move the mouse to
                           the "2.3ns" point, and the Scope displays the
                           value that the current signal had at that time.

            Slope:         Display the slope of the line between the
                           starting and current mouse positions, where
                           rise is measured in the units of the current
                           signal, and run is measured in seconds.

               Time        Display absolute or delta time, in seconds.

               Freq        Display delta time, in Hz (= 1/seconds).

               Signal      Display the value of the signal whose name is
                           highlighted, in Volts or Amps.  As you touch
                           this word, each signal is highlighted one by
                           one.  You can also select a current signal
                           by tapping its trace on the screen.

  12.  The word ON is a "power switch" for the simulation.  If you touch
       it, it changes to OFF and the simulation halts.  When you touch it
       again, simulation continues.  (In the circuit-diagram screen, this
       function is called Simulation in the Misc menu.)

  13.  When you touch Dump, the Scope writes out all of the data into a
       file in a standard format.  You may want to do this in order to
       use a more hefty data analysis tool with data generated by AnaLOG.
       The CNS 182 "View" program is one such tool, with a special "aload"
       command for loading AnaLOG dump files. MATLAB is another possibility;
       Michael Godfrey has written a tool to convert Dump output to 
       MATLAB format.

john [dot] lazzaro [at] gmail [dot] com