rehsd

As my W65C265S hardware build is coming along well, I would like to develop an operating system (OS) for it. While I have done miscellaneous 65xxx development over the years, my code has always been a mishmash of routines. The closest I have come to better understanding operating systems is implementing FreeDOS on my 286/386 builds, where I was adding core BIOS routines to support FreeDOS. So, can I hack my way through this and develop and operating system? Time will tell. So

Continuing my W65C265S project series, I am at a nice milestone where I have a second version of a PCB (actually, a pair of PCBs) -- with significantly expanded functionality from my first PCB. For more background on my work on this up to this point, check out rehsdonline.com/post/w65c265s-single-board-computer . My goal in this post is to work through the two PCBs in the rendering below. This post will be updated as I work through the design and build. [February 07, 2026] I

When I first started working with the W65C265SXB board, I was trying to get interrupts to work and was having no luck getting the interrupt service routine (ISR) to run. My setup was a simple momentary switch pulling down P41 (IRQB interrupt) or P64 (negative edge P64 interrupt). As I reviewed the sample LEDP72.asm that was included with the WDC Tools, I found vectors defined at the end of the file. Notice the Shadow_VECTORS section at $7EE0 and the vectors section at $FFE0

As I've been working on my W65C265S single-board-computer (SBC) project (see rehsdonline.com/post/w65c265s-single-board-computer ), one of the greater mysteries is the parallel interface bus (PIB). I've found limited information about the PIB, other than some basics in the '265 data sheet. I'm hopeful to get the PIB implemented in the latest phase of my '265 SBC project. Here, I will collect information that should be helpful in my goal of implementing PIB for a dual-265 SBC

It has been a few years since I have worked with the 6502 and 65816 processors. Most recently, my focus has been learning about FPGAs and developing my own FPGA PCB . Along the way, I designed some retro 286 and 386 systems, dabbled with a variety of microcontrollers, and learned more about PCB design. I thought it might be fun to build a single-board computer (SBC) based on the W65C265S microcontroller from The Western Design Center (WDC). This post will be updated as I wo

Over the past year, I took a shot at designing a Zynq-7000-based development board. I am now considering an update to my first board --...

Over the last few months, I have continued to experiment with my Zynq-7000 board . My board has been running well and is very stable. The...

I am hoping to get audio support for my custom Zynq-7000 development board. After a little digging into options, I am currently focusing...

Recently, I received a request to walk through the creation of a two-layer, through-hole PCB in EasyEDA Pro. As I considered what kind of...

As my custom Zynq-7000 board has been working fairly well (see my previous blog post ), I have been learning about PetaLinux. I am...

Recently, I have been working on different MCU and FPGA development boards. The FPGAs to this this point have been simpler, or older,...

I have a batch of Xilinx XC5215-PQ160AKMOO21 FPGAs. These are old FPGAs and it will be a challenge (if not impossible for me) to get one...

I am just beginning to work on a dev board for a Xilinx Spartan XC3S200AN-FTG256AGQ1413. I plan to use this page to capture information...

As part of my post on MCUs, I added a Lattice iCE40 FPGA to the mix. While I have done a little bit of work with FPGAs in the past, it...

I am starting to experiment with different microcontrollers (MCUs). I am hoping to learn about 8-bit, 16-bit, and 32-bit MCUs -- from a...

As I have gotten my 386 DX upper and lower motherboard PCBs working -- at least to the point of validating much of the design -- I am now...

Picking up from 80386 DX Build (rehsdonline.com), I am transitioning my 386 DX build to an EATX form factor, incorporating changes up to...