• Logisim home page
• Guide to Being a Logisim User
  • Beginner's tutorial
    • Step 0: Orienting yourself
    • Step 1: Adding gates
    • Step 2: Adding wires
    • Step 3: Adding text
    • Step 4: Testing your circuit
  • Libraries and attributes
    • The explorer pane
    • The attribute table
    • Tool and component attributes
  • Subcircuits
    • Creating circuits
    • Using subcircuits
    • Debugging subcircuits
    • Logisim libraries
  • Wire bundles
    • Creating bundles
    • Splitters
    • Wire colors
  • Combinational analysis
    • Opening Combinational Analysis
    • Editing the truth table
    • Creating expressions
    • Generating a circuit
  • Menu reference
    • The File menu
    • The Edit menu
    • The Project menu
    • The Simulate menu
    • The Window and Help menus
  • Memory components
    • Poking memory
    • Pop-up menus and files
    • Hex editor
  • Logging
    • The Selection tab
    • The Table tab
    • The File tab
  • Application preferences
    • The Template tab
    • The Tools tab
    • The International tab
    • The Experimental tab
    • The command line
  • Project options
    • The Canvas tab
    • The Simulation tab
    • The Toolbar tab
    • The Mouse tab
  • Value propagation
    • Gate delays
    • Oscillation errors
    • Shortcomings
  • JAR libraries
    • Gray Code Incrementer
    • Library Class
    • Simple Gray Code Counter
    • Gray Code Counter
    • Guidelines
  • About the program
    • GNU General Public License
• Library Reference
  • Base library
    • Poke Tool
    • Edit Tool
    • Select Tool
    • Wiring Tool
    • Text Tool
    • Menu Tool
    • Splitter
    • Pin
    • Probe
    • Clock
    • Text
  • Gates library
    • Constant
    • NOT Gate
    • Buffer
    • AND/OR/NAND/NOR Gate
    • XOR/XNOR/Even/Odd Gate
    • Controlled Buffer/Inverter
  • Plexers library
    • Multiplexer
    • Demultiplexer
    • Decoder
    • Priority Encoder
    • Bit Selector
  • Arithmetic library
    • Adder
    • Subtractor
    • Multiplier
    • Divider
    • Negator
    • Comparator
    • Shifter
  • Memory library
    • D/T/J-K/S-R Flip-Flop
    • Register
    • Counter
    • Shift Register
    • Random
    • RAM
    • ROM
  • Input/Output library
    • Button
    • Joystick
    • Keyboard
    • LED
    • 7-Segment Display
    • Hex Digit Display
    • LED Matrix
    • TTY
  • Legacy library
    • Logisim 1.0 D/J-K Flip-Flop
    • Logisim 1.0 8-Bit Register

Pop-up menus and files

The pop-up menu for memory includes four options in addition to the options common to all components:

• Edit Contents: Bring up a hex editor for editing the contents of memory.
• Clear Contents: Resets all values in memory to 0.
• Load Image...: Resets all values in memory based on the values found in a file using the format described below.
• Save Image...: Stores all values in memory into a file using the format described below.

The file format used for image files is intentionally simple; this permits you to write a program, such as an assembler, that generates memory images that can then be loaded into memory. As an example of this file format, if we had a 256-byte memory whose first five bytes were 2, 3, 0, 20, and -1, and all subsequent values were 0, then the image would be the following text file.

v2.0 raw
02
03
00
14
ff

The first line identifies the file format used (currently, there is only one file format recognized). Subsequent values list the values in hexadecimal, starting from address 0; you can place several such values on the same line. Logisim will assume that any values unlisted in the file are zero.

The image file can use run-length encoding; for example, rather than list the value 00 sixteen times in a row, the file can include 16*00 rather than repeat 00 sixteen times. Notice than the number of repetitions is written in base 10. Files produced by Logisim will use run-length encoding for runs of at least four values.

Next: Hex editor.