How do CV carts work?

[cbmeeks]

Ok, stupid question here. lol. Anyway, I'm really trying to learn the internal workings of the CV.

 

When I look at he cartridge port, I see what appears to be A0-A13 which gives 16k. Ok, next I see EN8/A/C/E. So, when power on how does the CV use those 4 lines compared to the 16k? And how were 24 or 32k carts made?

 

Thanks for any detailed info.

[+5-11under]

There's an A14, too, for 32K.

http://atarihq.com/danb/files/colecovision.pdf

[cbmeeks]

Ah I missed that. So does that mean 32k is the max cart size? How do the four extra lines work?

Thanks.

Edited April 24, 2015 by cbmeeks

[PkK]

32K is the max directly adddressable size. The extra 4 lines are chip enable signals for 8K segments (doing it that made way made some sense back when 32K carts had 4 8K chips in them. These days 32K carts have a single 32K or 64K chip in them, and need additional logic to handle the chip enable signals).

 

Philipp

[cbmeeks]

So how would a 32k or 64k chip work in the cart?

[+nanochess]

So how would a 32k or 64k chip work in the cart?

 

You would use an AND logic in the input for the 4 signals, or an array of 4 diodes expanding this:

 

 

For a 64K chip you tie the higher address to zero.