Anyone know what is this board?

[jonweiss]

I found this board in a Atari 800 I had in the attic. It was in the last slot of the computer. Does anyone know what this is? I couldn't find any information on the web about it. I think it might be a clock card. I have no software for it.

[fibrewire]

The part number for the big chip is MC6821P - a peripheral interface adapter for connecting M6800 CPU to peripheral devices. MSM5832RS - RTC... As if the oscillator and battery weren't a dead giveaway

[Rybags]

I'd say yes, not much other reason to have a battery other than keeping SRAM alive.

 

I found a datasheet match for a RTC58321 IC which is an RTC chip. There's other variants also like 58323.

 

The 6821 is a PIA. The RTC uses a 4-bit data bus and a few control lines which need to have latched values to function normally.

[fibrewire]

I was gonna say that!

[fibrewire]

pins 14, 15, 16 for PB4, PB5, PB6

MC6821P.pdf

[ovalbugmann]

Anyone know what is this board?

 

IDK, I though this was the atariage.com message-board, but in looking around the site it all looks totally different now. Hmmm.

[fibrewire]

Answers for 'New Forum Look' are covered here

[guus.assmann]

Hello,

 

It is a RTC.

And the parts used are the same as in a design I've made long ago.

I've attached the schematic diagram and the driver software for the design that I've made.

The datasheet for the clock chip should also be available. (And I will have it somewhere as well)

All data should enable you to use the parts.

 

BR/

Guus

Dos25_Clock.atr

[jonweiss]

Hello,

 

It is a RTC.

And the parts used are the same as in a design I've made long ago.

I've attached the schematic diagram and the driver software for the design that I've made.

The datasheet for the clock chip should also be available. (And I will have it somewhere as well)

All data should enable you to use the parts.

 

BR/

Guus

 

 

Thanks guys, I thought thats what it was. It's taking one of the slots so it doesn't have the full 48K of memory.

[sloopy]

get a 32k mem card for your 800, and then you will have 48k and the clock...

 

 

sloopy.

[+Stephen]

Or you could sell me the RTC I'll even throw in an extra 16kB RAM card if you need it to fill the void.

[puppetmark]

The datasheet for the clock chip should also be available. (And I will have it somewhere as well)

All data should enable you to use the parts.

 

Here is tthe datasheet for the clock chip:

 

 

MSM5832.pdf

[Defender II]

Let me know if you decide to sell it.

[fibrewire]

According to this the PIA 6821 is the same as the 6520A used in the Atari 800, although pin 35 & 36 seem to be switched.

 

Could another PIA be attached to the data bus in a plug in card to add more interfaces without disabling the existing Port A and Port B?

[guus.assmann]

Hello fibrewire,

 

Yes that can be done. And it's not too difficult.

But it would need a small change to the addressing of the original PIA.

Again. not difficult. But it does involve (intrusive) change of the Atari parts.

 

BR/

Guus

Edited July 25, 2013 by guus.assmann