I've been trying to download http://archive.6502.org/datasheets/mos_6520_pia_preliminary_undated.pdf which seems to point to internet archive.

Does anyone know if there is another mirror, as internet archive has been down for a few days now. They had a security incident and are still currently ...

I'm trying to build a Arduino based project to read/write to MOS6550 RAM (1024 x 4 bit)

Datasheet is here:
https://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/6550-datasheet.pdf

Looking at the datasheet there is sparse information on exactly what timing are needed and the logic. Read/Write ...

The clock - Sure, trivial to output a free-running clock from the ATmega, but is that what you want? The reality is that you'll have to synchronise the other signals to the clock


That is the one thing that's messing with my head. How to sync the clock. I'll try just a slow free running clock ...

Thanks, I was a bit puzzled by that. Good to know it can be run slower.

what exactly do you want to achieve in terms of functionality?

I've got a arduino mega 2560 so there are more than enough pins. I want to be able to r/w to the 128 bytes of RAM, and as a bonus be able to use the PA and PB I/O ports.

Will wire up the address/datalines etc to the use the full ...

Good point on the 3.3V and 5V Arduino's.

I've checked and have a 5V version. It sounds doable so will take a stab at getting the control lines and addressing all setup.

Time to take a deeper look into the datasheet.

I'm looking to start a project trying to connect a 6532 chip to an Arduino and before I go down the rabbit hole I want to first try and figure out on paper if this is even remotely doable.

I want to to be able to read/write to the RAM and use the I/O pins to drive something like LED's

Before you ...

Store $01, $02, ... $80 to address 0, with a delay between writes. Then store $00 to addresses $0001, $0002, ..., $8000, again with a delay between each. That will do exactly what you've described, but won't be capable of very much more.

This is exactly what I'm looking to do for the first ...

A bit more details on what I'm trying to do

The plan is build a 6502 tester where the program stored in ROM will loop and turn on the LED (connected via some latch/logic) connected to D0 on, then D1 on, D2 off, D3 on D2 off etc

And then repeat the same for A0 to A15. This way I can get some ...

Good point on 6522 - I didn't even think about this option yet and it might be the way to go.
That can be phase 2 of the project

Thanks for the info. I'll take a look at the primers and using phase 2 - at least this points me in the right direction.

I want to control all the LED"s individually so will need to use the latch.

Just starting off on the 6502 and thought a fun first project would be to hookup LED's to A0-A15 and D0-D7 and use a 74HCT574 to latch the LED's which will be controlled via code written to a ROM.

What I want to do is write some assembly to turn on D0 through D7, one LED at a time, which is easy ...

Perfect, thanks very much.

I've just built the RC6502-Apple-1-Replica PCB and populated with all chips (RAM, ROM etc)

Project link:
https://github.com/tebl/RC6502-Apple-1-Replica/tree/master/RC6502%20Apple%201%20SBC

Just fired it up and connected up a USB to the Arduino and it looks like its all working.
Wrote a quick hello ...