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 …
6502: Memory
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 …
6502: I/O Devices
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 …
6502: Memory Map and Address Decoder
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 …
6502: Power-on Reset
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 …
6502: Is My Crystal Oscillator Working Correctly?
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 …
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6502: A Journey Down Memory Lane
For the last six months or so of Covid lockdown I’ve been having fun following along with and expanding on Ben Eater’s breadboard computer projects. They are great educational projects and I’ve learned a lot of computer fundamentals along the way. There is also a subreddit with lots of helpful people and advice on building …
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