I worked on the Build 4 modifications over several weeks, partly because I was just playing around with what I had on hand when I started and partly getting sidetracked looking into why things happen instead of just getting on with the build. In this post I discuss troubleshooting the memory corruption issues I found. …
Continue reading “65816: Build 4 Troubleshooting 2 – Memory Corruption”
I worked on the Build 4 modifications over several weeks, partly because I was just playing around with what I had on hand when I started and partly getting sidetracked looking into why things happen instead of just getting on with the build. In this post I discuss one of those side investigations regarding the …
Continue reading “65816: Build 4 Troubleshooting 1 – It’s the PLD, or is it?”
I worked on the Build 4 modifications over several weeks, partly because I was just playing around with what I had on hand when I started and partly getting sidetracked looking into why things happen instead of just getting on with the build. In this post, I discuss modifying Build 4 in more detail. In …
Continue reading “65816: Modifying Build 4 as a 65816 Testbed”
I had just finished building and testing my fourth 6502 build, a barebones testbed for my new PLD based address decoder. With my PLD successfully tested, the build didn’t really have much use anymore, except testing new PLD designs in the future. Given that it was barebones I figured it would be fun to see …
Continue reading “6502/65816: Running a 6502 build with a 65816”
I ran into an interesting problem the other day trying to upgrade my 6502 build 4 to work with the 65816. I plan to write more on this in another post, but after just one minor change I got build 4 with a 65816 to almost startup my 6502-based Forth operating system. For some reason, …
Continue reading “6502: Coding – Just because it works doesn’t mean it’s correct”
I completed my fourth 6502 build the other day. It’s a barebones build, mainly intended to test my new PLD-based address decoding/interrupt request design. I didn’t need serial or keyboard support to test the PLD so haven’t included quite a bit of the I/O support that I had in build 3. I’m thinking that I’ll …
Continue reading “6502: My Fourth Build – Testing the New Programmable Logic Device”
I mentioned in my last post, Venturing Forth, that I ordered a programmable logic device to better refine my address decoding as my current circuit wastes about 16k on I/O. I worked up the new memory map and PLD files while waiting for the device to arrive. Then, as seems all too common with me, …
Continue reading “6502: Programmable Logic Devices – Address Decoder Revisited”
My daughters came home for the summer soon after my last post and as my work area is in their normally vacant bedroom, I chose to work more on the software side of things for the summer. Well, that turned into an adventure that’s kept me occupied for the last six months. They’ll be home …
After you’ve finished Ben Eater’s 6502 computer project, if not long before, as with me, you may be wondering about editor and assembler options for your 6502 coding work. Ben uses a basic Linux based editor and the VASM assembler throughout his project. If you are a regular Linux user you may be comfortable using …
With my second build, I’d successfully tested the hardware, memory and I/O devices I wanted to use in my third build, my planned handheld unit. Eager to move on, I quickly drew up a schematic and laid out a PCB for my planned design. Consistent with a handheld unit, I wanted to keep the PCB …
My first 6502 build, which followed Ben Eater’s 6502 computer project, uses two pretty pedestrian memory chips, an Atmel AT28C256 32k byte EEPROM and a 62256 32k byte SRAM. The EEPROM has a relatively slow 150 nanosecond access time. The SRAM access time is faster at 70 nanoseconds. The significance of these access times become …
My first 6502 build, which followed Ben Eater’s 6502 computer project, has a 16 character by 2 line LCD and a single red LED for output and four push button switches for input. Ben stopped his original video series with just a single push button, but I added three more as pictured on the front …
The 6502 microprocessor can address a 64k byte range. As a system designer you must split this address space between RAM, ROM and I/O according to your requirements. My first 6502 build, which followed Ben Eater’s 6502 computer project, used a straight forward memory map with 16k bytes of RAM (address range $0000-$3FFF), 32k bytes …
The WDC65C02 datasheet says that to initialize the microprocessor and start program execution the reset pin must be held low for at least two clock cycles after the power supply reaches operating voltage. In most cases if this is not done your 6502 based computer will not function properly. Ben Eater’s 6502 computer accomplishes this …
I enjoy recreating the component tests that Ben Eater performs in his electronics project videos. Sometimes my test results differ enough from Ben’s that I wonder if the component I’m testing is defective. More often than not the component is fine and I’ve either botched the test circuit or have set up the testing equipment …
Continue reading “6502: Is My Crystal Oscillator Working Correctly?”