README

Logisim components for implementing a HACK-like computer as described in the From NAND to Tetris course.

Dependencies

The only external dependency is logisim.jar. Since it's not available in the maven repos we need to add it manually before the first build:

mvn install:install-file -Dfile=${PATH_TO_LOGISIM}/logisim.jar -DgroupId=com.cbrunch -DartifactId=logisim -Dversion=2.7.1 -Dpackaging=jar

This needs to be executed just once.

Build

This project uses maven.

To build it, use the following command:

mvn package

The jar file is in the target directory.

Usage

Open Logisim and load the jar file from the Project -> Load Library -> JAR Library... menu.

Components

Bitmap display

The display follows the specification from nand2tetris. It is a 512 by 256 bitmap (that is, black and white only). It consist of 8192 16-pixel "segments".

Here are the pins from left to right:

• RST - Resets the display. Redraws it all in white. Works regardless of the state of CLK and LOAD.
• CLK - The clock. The display is updated only when the clock changes state from 0 to 1.
• LOAD - Idicates whether to update display (1) or not (0).
• ADDR - 13-bit address of the 16-bit segment to be updated. Address 0 is the top-left segment, 1 is next to it and so on.
• IN - 16-bit data in. The bits are copied over the specified segment. Bit 1 means foreground color (black), while 0 means background (white).
• OUT - 16-bit data out. The data that is currently stored (and displayed) in the specified segment.

If the LOAD is 1 when the CLK goes up, all the 16 pixels in the specified segment are updated at once.

RST works with priority. If it's 1, the display is cleared (all white) regardless of the state of the other pins.

Here is how it looks:

Author

Ivan Toshkov