u/2E26

One major part of this project is done. Next, I need to finish programming my PIC16F877A to write code to the EEPROM. Once I can get this computer running some rudimentary programs, the next step is to install the serial port add-on.

Other improvements I hope to achieve:

- write my own monitor and boot loader program

- expand RAM by reducing ROM to 8K

- increase allocatable RAM by coming up with a better address bus handler.

- interface with my PIC16F877A and use it to read programs from external media. Options include SD cards, paper tape and punch card, even floppy disks if I can figure out how to work with them

- USB support for keyboard interface.

- collect underpants

- ???

- profit

Last fall, I bent some scrap aluminum to form a chassis and screwed it together. I went on deployment and returned. Now, I'm working on finishing it up so I can fire up some tubes again.

HV: Triad 35 VA isolation transformer (120v - 120v) feeding bridge rectifier (1N4007 x4). Two series 51 ohm resistors and two 120 uF capacitors. Bleeder resistor is 10K x2 in series. B- rail tied to chassis via 100K or so resistor and 0.1 uF capacitor.

LV: Radio Shack 12.6 VCT 3A transformer. Powers pilot light LED via 6v winding. Switch selected output for 6 or 12 volts, with LED indication for voltage selected. Indicator LEDs are different colors to differentiate 6 or 12 volts.

Output: GX-16 aviation type connector, 7-pin. This will become my standard for tube electronics. If I require higher filament current I may go home and rethink my life.

First, a link to my code repository: 2E26/PIC16-Code-Repository: Code written for PIC16 microcontrollers. All programs are intended to work with x86 and 6502 platforms via serial data transfer.

It was assumed that, by using XC8 compiler, I wasn't actually working in assembly. I changed to MPASM just to see what the difference was, as I've read much about how it was superior to XC8/PIC-ASM. For all I can tell, it's not any different except for assembler directives and other meta-code. The assembly language is still there. My last post was deleted because one of the mods decided I was lying about writing in assembly.

That being said, my latest projects are here for scrutiny. PIC assembly isn't as familiar to me as 6502, as I did some in college with emulators. However, this is my first go at actually putting bits in chips, and everything I've done so far works. I've played with x86 assembly for far longer, and even have more experience in 6502 than PIC. Still, PIC is more fun because it's easier to unite it with electronics, which I'm much better at than computing.

What you'll see if you look at my code is a simple serial monitor. How simple? It echoes what you type in it back to you. That's it. It tests the capability of the MCU to send and receive data from the serial port instead of just send an 'S' over and over. I also wrote a USART library and wrote the same program again with it. I'm probably going to get used to writing libraries for hardware functions in the PIC.

My next moves will be to begin programming EEPROM chips for the 6502 computer. For now, I intend to build it stock (per the wiring diagram on Eater.net/6502 ) and later upgrade to more RAM and a smaller ROM space. My idea is to make the ROM space a boot loader to put larger programs into RAM and then play with them that way. The PIC will be carried on as a peripheral for me to explore other ways of getting code into the 6502 computer.