Correct TIA pinout

[Wickeycolumbus]

Does anyone know the correct way to enable the TIA chip? I know that there are 4 chip selects, CS0, CS1, CS2, and CS3 on pins 24, 23, 22, 21 respectively but many pinouts I see online have different information as to weather they are active high or low. Here are some examples:

 

http://atarihq.com/danb/tia.shtml

http://www.atarimax.com/jindroush.atari.org/2600ctia.html

http://amazingdiy.files.wordpress.com/2011/07/atari2600_tias.jpg

http://www.atariarchives.org/dev/tia/images/38.gif

 

If anyone knows the correct way to enable it, I'd be very thankful. I'm trying to restrict it's address range to $0000-$003F.

 

Thanks!

[+batari]

Schematics show CS1 is high and the rest low. The address range is not normally restricted to $00-$3F, however. Only A7 and A12 are decoded and connected directly to CS3 and CS0, respectively. If you want to further restrict the address range you will need to add logic to do that.

[SeaGtGruff]

As batari mentioned, CS1 is active high, whereas /CS0, /CS2, and /CS3 are active low. To expand very slightly on what he said...

 

CS1 is connected to power (always high if the power is on), and /CS2 is connected to ground (always low), so they don't contribute anything to the addresses.

 

/CS3 is connected to A7 and should be low to address the TIA.

 

/CS0 is connected to A12 and should also be low to address the TIA.

 

However, the TIA schematics are a bit confusing, as they don't specify what the chip select pins are connected to, and there's a note on sheet 2 (where the address decodes are shown) stating that CS1 and /CS3 were deleted in chip revision E. That would make sense if CS1 and /CS3 are connected to power and ground, respectively, since they would always be high (CS1) or low (/CS3) as long as the machine is turned on, hence there's not much point in checking them. Yet the 2600 schematics show that /CS2 is connected to ground and /CS3 is connected to A7, so it appears that perhaps the note on TIA schematics should have read that CS1 and /CS2 were deleted in chip revision E. Note that the TIA schematics also show the pin numbers for L0 (LUM0) and L1 (LUM1) as being switched around from what all other sources show-- which has no bearing on the address issue, but does suggest that the TIA schematics may contain a "typo" or two.

 

Of the remaining address lines, only A0 through A5 are connected to the TIA. A0 through A5 are decoded for the write addresses, but only A0 through A3 are decoded for the read addresses.

 

There's no way to restrict the TIA's address range to $0000 through $003F inside the TIA itself. You'd need to do it outside the TIA, presumably by checking A6 through A15 and redirecting the address access request to some other destination if any of those address lines are 1, and letting the request go through to the TIA only if all of those address lines are 0. I have no idea how you would go about doing that, though-- I'm not a hardware guy-- but I assume it would involve some sort of "internal surgery" or hardware modification to the 2600 (i.e., I don't see how you could do it with just some sort of special cartridge since the 6507 and TIA connections are inside the console and-- as far as I know-- can't be "trapped" by the cartridge). Of course, there are no pins on the 6507 for the A13 through A15 address lines, so I don't know how you could prevent the TIA from accessing "mirrors" above $1FFF.

[Wickeycolumbus]

Thanks for the information guys. I was able to get it to work. I'm using a PLD to control /CS2 based on A6-A15 (excluding A7 and A12, which were left connected directly to the TIA). This was for my overclocked/expanded 2600 project.

[SeaGtGruff]

Thanks for the information guys. I was able to get it to work. I'm using a PLD to control /CS2 based on A6-A15 (excluding A7 and A12, which were left connected directly to the TIA). This was for my overclocked/expanded 2600 project.

Clever solution!

[DanBoris]

Does anyone know the correct way to enable the TIA chip? I know that there are 4 chip selects, CS0, CS1, CS2, and CS3 on pins 24, 23, 22, 21 respectively but many pinouts I see online have different information as to weather they are active high or low. Here are some examples:

 

http://atarihq.com/danb/tia.shtml

http://www.atarimax....g/2600ctia.html

http://amazingdiy.fi...ri2600_tias.jpg

http://www.atariarch...a/images/38.gif

 

If anyone knows the correct way to enable it, I'd be very thankful. I'm trying to restrict it's address range to $0000-$003F.

 

Thanks!

 

Never noticed the variations in the CS pins on the different sites, glad mine was correct!

[Wickeycolumbus]

Never noticed the variations in the CS pins on the different sites, glad mine was correct!

 

Your site is a great resource, I go there quite often for info like this