SAM Port

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SAM Port

Postby wmmullaney » Feb Tue 14, 2012 12:14 am

Hey everyone, I was thinking a port of the Apple II SAM to the R1 would be really cool, especially for demonstrations. Does anyone know how one go about this? It seems like it should be possible using cowgod's projects.

Thanks
Adventures with the 6502 - Retro computing from a highschooler's perspective.
wmmullaney
 
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Re: SAM Port

Postby palbeda » Mar Thu 08, 2012 9:18 am

Hi all,

Well, I could draw up the hardware easily I am sure, the hardware is not at all complex. Basically it contains of an address selector (or make it respond to EVERY write to CXXX), a simple D/A converter and an audio amplifier chip. To port the software, it becomes easier if you use the slot 4 port address (default SAM slot on the Apple II). There is a binary file in memory and the rest is a Basic program I think.

Would be VERY cool to port SAM.

Anybody interested to do this together?

Best regards,

Peter
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Re: SAM Port

Postby wmmullaney » Mar Sat 17, 2012 10:43 pm

Cowgod has designed the audio card and BASIC port already: http://cowgod.org/replica1/

It shouldn't be hard. I know the Apple 1 architecture well enough, but nothing of the Apple II. I would be glad to try learning if anyone else wanted to collaborate.

I have the SAM disk image if anyone needs it.

Will
Adventures with the 6502 - Retro computing from a highschooler's perspective.
wmmullaney
 
Posts: 10
Joined: Jan Tue 04, 2011 1:25 pm

Re: SAM Port

Postby palbeda » Mar Wed 28, 2012 3:30 pm

Hi,

I am currently reverse engineering the SAM hardware. The design is very simple.

The eight data lines are attached to a 74LS273, containing 8 D-flipflops, which are clocked by the Device select line of slot 4.

The actual D/A conversion is done with a DAC0808 IC, which is amplified by a LM380 OpAmp, which is attached to the Apple II speaker.

A point of attention is that the card uses plus and minus 12 Volt. If you do not use an ATX powersupply, that could be a problem.

I am considering to use another A/D design I found on the Internet using an octal latch and a buffer IC and a resistor network.

Best regards,

Peter
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Re: SAM Port

Postby wmmullaney » Apr Sun 15, 2012 5:57 pm

Interesting, do you have an Apple II schematic you could send me? I haven't been able to find one.

I wasn't aware that a DAC was even involved, that the sound was dithered directly from one of the flip flops. At least that's what my replica sound card looks like.

Thanks for looking into it, I'm looking forward to the project results :D

Will
Adventures with the 6502 - Retro computing from a highschooler's perspective.
wmmullaney
 
Posts: 10
Joined: Jan Tue 04, 2011 1:25 pm


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