The Elements of Computing  Systems / Nisan & Schocken / www.idc.ac.il/tecs  

Project 3: Sequential Chips

Objective: Build all the chips described in Chapter 3. The only building blocks that you can use are primitive DFF gates, chips that you will build on top of them, and chips described in previous chapters.

Resources: The only tool needed for this project is the hardware simulator supplied with the book. All the chips should be implemented in the HDL language specified in appendix A. As usual, for each chip we supply a skeletal .hdl program with a missing implementation part, a .tst script file that tells the hardware simulator how to test it, and a .cmp compare file. Your job is to complete the missing implementation parts of all the supplied .hdl programs.

Contract: When loaded into the Hardware Simulator, your chip design (modified .hdl program), tested on the supplied .tst file, should produce the outputs listed in the supplied .cmp file. If that is not the case, the simulator will let you know.

Chip (HDL)	Function	Test script	Compare file
DFF	Data Flip-Flop (primitive)
Bit	1-bit binary cell	Bit.tst	Bit.cmp
Register	16-bit Register	Register.tst	Register.cmp
RAM8	16-bit / 8-register memory	RAM8.tst	RAM8.cmp
RAM64	16-bit / 64-register memory	RAM64.tst	RAM64.cmp
RAM512	16-bit / 512-register memory	RAM512.tst	RAM512.cmp
RAM4K	16-bit / 4096-register memory	RAM4K.tst	RAM4K.cmp
RAM16K	16-bit / 16384-register memory	RAM16K.tst	RAM16K.cmp
PC	16-bit Program Counter	PC.tst	PC.cmp

The Data Flip-Flop (DFF) gate is considered primitive and thus there is no need to build it: when the simulator encounters a DFF gate in an HDL program, it automatically invokes the built-in tools/builtInChips/DFF.hdl implementation.

The directory structure of this project: When constructing RAM chips from smaller RAM chips, we recommend using built-in versions of the latter. Otherwise, the simulator may run very slowly or even out of (real) memory space, since large RAM chips contain tens of thousands of lower level chips, and all these chips are kept in memory (as software objects) by the simulator. For this reason, we have placed the RAM512.hdl, RAM4K.hdl, and RAM16K.hdl programs in a separate directory. This way, the recursive descent construction of the RAM4K and RAM16K chips stops with the RAM512 chip, while the lower-level chips from which the RAM512 is made are treated as built-in (since the simulator does not find them in this directory).

Steps: We recommend proceeding in the following order:  

0.      The hardware simulator needed for this project is available in the tools directory of the book’s software suite;

1.      Read Appendix A (Hardware Description Language), focusing on sections 6 and 7;

2.      Go through the Hardware Simulator Tutorial , focusing on parts IV and V;

3.   Create a directory named projects/03 on your computer and extract project 03.zip to it (while preserving the directory structure embedded in the zip file).  Build and simulate all the specified chips.