BuildSOC

Building the SOC

The soc project is meant for simulating the complete system including peripherals. This project can boot the Bios and MSDOS within Modelsim and create VGA output signals.

Of course the soc project also uses the microcode memory file which we build before. The test bench and simulation script for this project is located in bench/soc.

Instead of running tests we will now boot the Bios and MSDOS. All the binary ROMs and disk images for this are contained in the bin directory. This directory should be used when referring to binary files from within source code.

The Bios could be compiled from scratch. Bios source code and compiled images are stored in the bios directory. Currently it contains the source code of the pcxtbios25 by Miles (1987) and Petrosky. See the readme file within the subdirectory for license and more info. All necessary tools and the make file (make.bat) for compiling the bios are included. However these tools are 16-bit and do not run on modern Windows systems. DOSBox can be used for running these tools. (See http://sourceforge.net/projects/dosbox/)

The MSDOS 6.22 floppy image is also located in the bin directory. This floppy image is borrowed from the fake86 project. (http://fake86.rubbermallet.org/)

The soc project can now be compiled and simulated with Quartus/Modelsim. The simulation results are written to project/soc/simulation/modelsim/ directory. The following files are created by the simulation:

• runlog.txt contains executed opcodes and register values
• memlog.txt contains memory access info
• vgalog.txt the vga signals (only 1 bit per color)

OsocDasm can be used to add assembler mnemonics to the memlog.txt simulation results. VGASim can be used to produce a graphical image from the vgalog.txt signals.