XTAL clock and 2A03

As Michael says, you'll find this tricky to get right without some way of looking at the waveform coming

out.

This worked with an ordinary 16MHz AT-cut processor crystal and a 2N3904 transistor. I've biased it to

swing around 1.5V, which would suit a TTL level input. If it's a pure CMOS input, you'd want to move that

up to 2.5V (by changing the base bias resistor).

The collector resistor is a compromise. Increasing it increases the gain, but it doesn't then drive so

well. In my case, 3.3k was better than 1k or 4k7 [I didn't experiment any further].

For what you're doing with the 6502 clone, couldn't you just generate the clock from the Arduino and run

everything at whatever speed it can manage to generate the signals at. Does it matter if you see it

running at only a tenth of the normal speed, or whatever you get? The original 6502 parts were static and

there was no minimum clock speed, so I don't imagine this device would be too fussy either. You could get

the Arduino to control the reset too.

Edit

Not only do you need a way of looking at the waveform, you also need to know how to use it properly. I had the 20MHz bandwidth limit on. This is what it looks like without

so my circuit isn't producing a very nice waveform.

As Michael says, you'll find this tricky to get right without some way of looking at the waveform coming

out.

This worked with an ordinary 16MHz AT-cut processor crystal and a 2N3904 transistor. I've biased it to

swing around 1.5V, which would suit a TTL level input. If it's a pure CMOS input, you'd want to move that

up to 2.5V (by changing the base bias resistor).

The collector resistor is a compromise. Increasing it increases the gain, but it doesn't then drive so

well. In my case, 3.3k was better than 1k or 4k7 [I didn't experiment any further].

For what you're doing with the 6502 clone, couldn't you just generate the clock from the Arduino and run

everything at whatever speed it can manage to generate the signals at. Does it matter if you see it

running at only a tenth of the normal speed, or whatever you get? The original 6502 parts were static and

there was no minimum clock speed, so I don't imagine this device would be too fussy either. You could get

the Arduino to control the reset too.

Edit

Not only do you need a way of looking at the waveform, you also need to know how to use it properly. I had the 20MHz bandwidth limit on. This is what it looks like without

so my circuit isn't producing a very nice waveform.

I ended up putting the xtal back on the original board and getting the clock off of that but I'll have to look at this in more detail when I have time.

Generating the clock from the Arduino was my first thought but I heard older chips might not persist the state of the registers if you run them too slow, also the 2A03 is a sound chip as well. My end goal is to use the sound chip part and I assumed the sound generation part would need the right clock to sound right.