Breaking News: A working pause button for Atari 2600

[+batari]

Great that you solved the issue.

 

However, I don't believe it's correct that RDY should not be asserted on write cycles - From what I have read, it is perfectly safe to do so, but what actually happens is the 6507 just won't pause until the writes complete. It's true that the 6507 does not have phi1, but maybe if you only pause on write cycles, maybe the timing isn't strict.

 

Here is my proposal for a poor man's pause switch: connect a switch between pin 3 of the TIA (RDY) and pin 26 of the 6507 (R/W#). On my 4 switch, these pins are right across from one another so it would be really easy to try. Maybe it won't be as reliable but if my theory is correct, it should work reasonably well.

I was tired when I posted this and overlooked that R/W# is not an open drain output so you need a diode in there. TIA pin 3 is open drain so no problems here.

 

That is:

              	SW
6507 Pin 26 --|<|--/ --- TIA pin 3

 

I just tried it myself and it works 99% of the time. Maybe with a debounce capacitor it could work nearly 100%.

 

EDIT: Never mind, on some games it works maybe 80% which is not good enough.

 

 

Tangential request: Would you mind briefly clarifying the purpose/function of this diode for those of us to whom the term "open drain" has meant only "success with a plunger" for the past 20 or so years?

Open drain means the output is the drain pin of a MOSFET that is left open. An open drain output has two states: 0 and Z (floating.) To output a 1, you run a pullup resistor on the output. The advantage of open drain is that you can connect outputs together without contention and they perform an AND.

 

R/W# on the 6507 is not open drain, so a diode as above will come close to that by only pulling low but when R/W# is low, otherwise the diode is reverse-biased and nothing will happen.

[Curt Vendel]

There was an article on how to do this very thing in an old videogame magazine, did you base it on that very same circuit, it looks familiar.

 

 

 

 

Curt

[BigO]

Great that you solved the issue.

 

However, I don't believe it's correct that RDY should not be asserted on write cycles - From what I have read, it is perfectly safe to do so, but what actually happens is the 6507 just won't pause until the writes complete. It's true that the 6507 does not have phi1, but maybe if you only pause on write cycles, maybe the timing isn't strict.

 

Here is my proposal for a poor man's pause switch: connect a switch between pin 3 of the TIA (RDY) and pin 26 of the 6507 (R/W#). On my 4 switch, these pins are right across from one another so it would be really easy to try. Maybe it won't be as reliable but if my theory is correct, it should work reasonably well.

I was tired when I posted this and overlooked that R/W# is not an open drain output so you need a diode in there. TIA pin 3 is open drain so no problems here.

 

That is:

          		SW
6507 Pin 26 --|<|--/ --- TIA pin 3

 

I just tried it myself and it works 99% of the time. Maybe with a debounce capacitor it could work nearly 100%.

 

EDIT: Never mind, on some games it works maybe 80% which is not good enough.

 

 

Tangential request: Would you mind briefly clarifying the purpose/function of this diode for those of us to whom the term "open drain" has meant only "success with a plunger" for the past 20 or so years?

Open drain means the output is the drain pin of a MOSFET that is left open. An open drain output has two states: 0 and Z (floating.) To output a 1, you run a pullup resistor on the output. The advantage of open drain is that you can connect outputs together without contention and they perform an AND.

 

R/W# on the 6507 is not open drain, so a diode as above will come close to that by only pulling low but when R/W# is low, otherwise the diode is reverse-biased and nothing will happen.

Okay, got it now. Thanks.

 

Open drain outputs tied directly together act as an AND? . . . ah, yes, the group will always float (logic HI) unless any one or more of the outputs goes to zero then the group will be pulled down to 0. Anyone smell cobwebs burning or is it just me?

 

 

 

 

[vtrucco]

I just tried it myself and it works 99% of the time. Maybe with a debounce capacitor it could work nearly 100%.

 

EDIT: Never mind, on some games it works maybe 80% which is not good enough.

 

Try to pause for a "long" period, like 2 minutes or more. Your number will drop to 10%

[vtrucco]

http://hackaday.com/2010/02/23/add-pause-button-to-the-atari-2600/

 

Thanks again yuppicide

[Atari Dogs]

I can't remember. Does the Flashback have a pause button?

[Curt Vendel]

B/W switch works as a pause button for those programs that use it

 

 

 

 

Curt

 

I can't remember. Does the Flashback have a pause button?

[alex_79]

Nice mod! :thumbsup:

 

Do you think the circuit will work with a 74HCT00 instead of 74LS00?

 

How much difficult would be to disable audio and video when the game is paused like on the Onyx Junior console?

[vtrucco]

Nice mod! :thumbsup:

 

Do you think the circuit will work with a 74HCT00 instead of 74LS00?

 

How much difficult would be to disable audio and video when the game is paused like on the Onyx Junior console?

 

HC and HCT doesn't work. So far only LS.

 

To disable audio and video is pretty simple. Attach 2 diodes, catode pins in our pause switch. One diode you connect at TIA pins 12-13 and the other diode in composite video output

[alex_79]

HC and HCT doesn't work. So far only LS.

 

To disable audio and video is pretty simple. Attach 2 diodes, catode pins in our pause switch. One diode you connect at TIA pins 12-13 and the other diode in composite video output

 

Thank you!

I will try it on one of my consoles.