First iteration

 As Perifractic would say, hello chip dippers.

I worked on a version 1 of my breadboard 6502 last week. Sorry for now posting about it earlier. I opted to have some LEDs on the address and data bus for show. The hard-coded data lines 0xEA worked as expected. But as I increased the number of chips on the board, the ROM, and the RAM and the PLD (for decode logic), things started not to work so nicely. Stay tuned!

6502 with LED and Ben Eater's clock module

Testing the 6502 with hardcoded EA

Testing the 6502 with an EEPROM and a simple program


Comments

Post a Comment

Popular posts from this blog

To PLD or not to PLD

Image
When I start something interesting, I tend to overdo it. I originally contemplated using standard gates for my glue logic. But then chose to go the EEPLD (Electrically Erasable Programmable Logic Device) route. Wow, was I ambitious? Not only I was to build the 6502 single-board computer from the ground up, but I had to also get to know PLDs up close and personal at the same time. Well, it turns out it's not all that hard, if you find the right tutorials on the web, and if you have a precise memory map defined. I had this really particular memory map planned. But for my second iteration of the SBC, I opted to go simply and work my way up.  The map, for now, is 32K ROM, 16K IO space, and 16K RAM. This will change in the future. And this is the beauty of PLDs, there is no need to rewire anything. It's just the software that needs changing. I chose the ATF22V10C, a G22V10 equivalent, because of it's many input and output options: 12 dedicated inputs, and 10 configurable input/o...
Read more

First things first

Image
Before starting my adventure, I needed to do 2 things. Reorganize my lab space, and buy the necessary components. I wasn't quite ready to start my project, space-wise, as my office/lab was a mess and all my existing components were all thrown in various bins haphazardly.  Step one , reorder the furniture and optimize my desk space. Easier said than done, but I managed to do it in less than a day. Keep in mind that my "office" was also a dumping ground for everything else in the apartment. So I made some hard choices on what had to go and what stayed,  Mari Kondo style. It's not perfect, but it's a start. The following day, I sorted all my components, mostly because I was curious to find out what I had. And hold and behold, I had many unnecessary duplicates. That's what happens when you let me loose in my local electronics store without a shopping list or a plan. Step two , order the components needed. I chose Mouser because they carried the WD65C02 microproc...
Read more

TRS80 Model III Keyboard on my 6502 SBC

Image
The time has come to add a keyboard. I scrounged up an old Radio Shack TRS-80 Model III last year. Alas, it arrived broken. The tube was completely smashed! Thanks, UPS! So I decided to repurpose the microcomputer to become my future casing for the 6502 SBC. Not sure what I'm going to do for the final display. I did get my hands on some TMS9918 chips and the Parallax Propeller. But that's another post for another time. For now, the keyboard circuit is all done. It's fairly simple and the 8x8 keyboard matrix is directly connected to port A and port B of a second VIA chip. It did take me a while to map out the keyboard matrix. What is need about this keyboard is the integrated reset button. TRS-80 Model III Keyboard Matrix 12KE010C (or is it I2KEOIOC ?) ALPS ELECTRIC CO., LTD. JAPAN 20 pin connector 9 10 11 12 13 14 15 16 1 @ A B C D E F G 2 H I J K L M N O 3 P Q R S T U V W 4 X Y Z 5 0 1 2 3 4 5 6 7 6 8 9 : * ; + , < - = . > / ? 7 Enter Clear Break Up Down Left Right S...
Read more