Sorry if this is a newbie question. Let's say I have a VIA port attached to I/O pins of a micro-controller like ATMega128P such as an Arduino.

The VIA would have port A set as inputs and the Arduino would be outputs.
Now, what would happen if I accidentally set the VIA port A as outputs too and the ...

I haven't read every response but I thought I would throw my $0.02 in.

For my project, I plan on using the Pico9918. Which is a drop-in replacement for the TMS9918. However, it has some extra advantages. First, it's somewhat affordable (relatively speaking) at $35 before shipping. However, it seems ...

Very helpful, thanks!

I'm connecting two NES controllers to one VIA (65C22).

For those that don't know, the NES controllers essentially have a simple shift register in them. You set the latch pin, then clock it 8 times and you will get the 8-bit value of the buttons.

Since I want to drive two of them, I was thinking ...

The VIA's SR (shift-register serial port) is confined to using CB2 for data and CB1 for clock. If the clock is controlled by a VIA timer, it will be T2. There are quite a few modes of operation for each; but as is the case also with microcontrollers, the various timers and pins have limitations in ...

Hello.

I found this schematic on how to drive a simple 3-bit DAC with a VIA (CB2).

http://wilsonminesco.com/6502interrupts/index.html#3.3

However, I was wondering if I could do the same thing with CA2. I'm reading over the data sheet but I'm just not getting how all of the timers work or I'm not ...

Thanks again.

I'm going to start a separate thread on the speaker. I'm not sure if that simple 9 bit DAC will work on Port A so I might have to swap the two ports.

Something like this?

I'm struggling with how the /IRQ is going to work with the three devices. I can eliminate one of the VIA's from the /IRQ and that would leave a UART and VIA (PS/2, LCD). It would be really nice if I could use the PS/2 and get serial interrupts together.

I was going to use the ...

From a VIA.
I plan on putting a shift register between the VIA and the ATMega which uses four pins of Port A. Then the other four pins will control the LCD registers, etc.

As for the PS/2, just straight 8 pins from the ATMega.

Attached is the unfinished schematic so far.

OK. Great!

But hoes ...

Oh, I see what you mean. Yeah, I completely missed that!

Hmm, I will have to think about that as I have already used up all my pins on that VIA. (not totally sure how CA(B)1/2 work).

And yeah, I was going to have the AVR decode the key strokes and send the bytes over so the 6502 only has to read ...

I'm not sure I know what you mean.

From a VIA.
I plan on putting a shift register between the VIA and the ATMega which uses four pins of Port A. Then the other four pins will control the LCD registers, etc.

As for the PS/2, just straight 8 pins from the ATMega.

Attached is the unfinished schematic so far.

Thanks for the information. After some research, I decided to go with an ATMega328P in my design. It will double-duty as a power on reset, debouncing some buttons, resetting chips, and handling the PS/2.

OHHH!!!

DUH. That makes a lot more sense. It's literally an LED like any other LED I've connected to breadboards a million times. Obviously, I need to do a little math but more than likely, I will just try some common R values and see what brightness I like. In fact, I have some smaller, cheaper ...

although if you're feeding it from batteries and need maximum battery life, a switching regulator operating in a constant-current mode would be good, not throwing away some of the energy by just warming up a resistor.

I like the idea of a LDO voltage regulator.

Maybe something like this?

https ...