Where thoughts show up as words
Fetch, and more Initial design goal was not to have a split fetch unit that does more than what fetch is supposed to do. The fetch unit in tinysys currently handles the following: Upon reading an instruction, it decoded and injected into a FIFO that the execute logic will pull from, which lets the fetch […]
Recap of arbitration As you will recall from part four, we have an arbiter that sits between SDRAM and devices that require access to it, serving read and write request separately, and providing somewhat fair share of the access. We can visualize that mechanism as a diagram like so: Thanks to the arbiter, the two […]
Hardware devices There are several physical devices on the tinysys carrier board. They require either one-way or two-way communication, each with its own bus type. The audio device uses an I2S bus to receive audio data from the FPGA fabric, whereas the SD Card uses SPI. Above all of this lives a software layer that […]
Previously on tinysys Last time I wrote some overviews about tinysys to slowly introduce the system, but I haven’t fully covered what it is that I am aiming to accomplish with a custom OS and a custom system design. In this part I will start doing that, and go bit by bit until we get […]
Multitasking on tinysys I wanted the hardware to be able to run more than one task at the same time (at the very least the device handlers and one or more other tasks), which meant that at the very least there had to be some kind of timer interrupt mechanism supported at CPU level. Luckily […]
Software-first approach Since I’m a software developer, tinysys was designed to be something that I can simply plug in and upload an ELF file onto, and not care about having it crash in a way that’s unrecoverable. Now that I think about it, I probably wanted a retro computer from the 80s but with a […]
I have been using and programming computers for about 40 years now, and I’ve been missing the 80s style computers, yet I like the modern day approach to computers and operating systems in general. So I thought, why not build something that has limited capabilities, but is also able to run binaries generated by modern […]