Thursday, September 29, 2016

NESDev - Hardware Implementation

I'm taking a small break from the Nerdy Nights tutorials and looking ahead to the hardware implementation of this project.  It has been my understanding that in order for me to write my own code onto a cartridge's ROM chip, I would need to get my hands on an EPROM programmer.  Thankfully, the University I study at happened to have one:

I spent a few hours with my professor teaching ourselves how it worked using a GAL chip to create some basic logic gates.  Fortunately, even as outdated as this programmer is, there was still software available for it online for Windows XP (at the verrrry bottom of the download list).  It took some effort before we were able to get the programmer into a working state.

 Thankfully, my research brought me to a a great "how-to" article on the ROM programming process by The Poor Student Hobbyist.  It looks as though the process of actually programming ROM chips and adding them to the cartridge PCB will be quite simple; the trick will be determining what size EPROM chips I will need for my CHR and PRG files.  It looks as though 128k and 32k size chips were popular for most NES cartridges at the time (source).  Which one I will need will naturally depend on the size of my game.  Either way, most of the EPROM chips used in these cartridges are compatible with this programmer, so I should not face any issues with equipment.

However, the concept of mappers are coming up again.  It might be time to write about them, either in an edit to this post or the next one.

Back to programming.


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