NTSC/PAL/SECAM detection accuracy

[+SpiceWare]

 

Back in 2015 @ZackAttack suggested using a timer in the ARM to detect if a 2600 was NTSC or PAL. Basically the ARM is fast enough to detect the difference in clock speeds between the NTSC and PAL consoles. While working on Draconian I decided to try this out and it was successful.

 

While I was adding ARM timer support to Stella @alex_79 pointed out that the clock for SECAM was different from both NTSC and PAL. Knowing that, I was able to update the routine detect between all 3.

 

The first game that used this auto-detection was Draconian. Because I didn't know how accurate the detection was I left in the TV-Type menu option so the player could change it if needed.  

 

The detection's now been in use for 3 years, so I'm wondering how accurate it has been because it would be really nice to remove the TV-Type menu option from Frantic and free up some valuable ROM space.  So let me know how well this works on your Atari. If you need the ROMs for your Harmony you can find them here:

 

• Draconian final ROM (blog entry)
• Frantic (reply 404)

 

If it fails then please run the NTSCvsPAL2 ROM found here and post what TV standard your 2600 is for, and what value was returned.

[Andrew Davie]

No fair. I thought it was impossible.

Neat bit of thinking!  I'd love a 6507 solution....

[+SpiceWare]

36 minutes ago, Andrew Davie said:

No fair. I thought it was impossible.

Neat bit of thinking!  I'd love a 6507 solution....

Would probably need to add a clock/timer into the cartridge. If you'd like more info on how it works with the ARM check this topic and its replies.

 

 

[Andrew Davie]

2 minutes ago, SpiceWare said:

Would probably need to add a clock/timer into the cartridge. If you'd like more info on how it works with the ARM check this topic and its replies.

 

 

 

2am here time for bed. My guess would be you just write code that puts known values on the address buss and then in the ARM code you time the difference between the address values. That would give you the frequency of the 6507.  I'll read the thread tomorrow

 

[+sramirez2008]

8 hours ago, SpiceWare said:

 

Back in 2015 @ZackAttack suggested using a timer in the ARM to detect if a 2600 was NTSC or PAL. Basically the ARM is fast enough to detect the difference in clock speeds between the NTSC and PAL consoles. While working on Draconian I decided to try this out and it was successful.

 

While I was adding ARM timer support to Stella @alex_79 pointed out that the clock for SECAM was different from both NTSC and PAL. Knowing that, I was able to update the routine detect between all 3.

 

The first game that used this auto-detection was Draconian. Because I didn't know how accurate the detection was I left in the TV-Type menu option so the player could change it if needed.  

 

The detection's now been in use for 3 years, so I'm wondering how accurate it has been because it would be really nice to remove the TV-Type menu option from Frantic and free up some valuable ROM space.  So let me know how well this works on your Atari. If you need the ROMs for your Harmony you can find them here:

 

• Draconian final ROM (blog entry)
• Frantic (reply 404)

 

If it fails then please run the NTSCvsPAL2 ROM found here and post what TV standard your 2600 is for, and what value was returned.

Tested the Frantic ROM for auto detection on four of my consoles (below) and each one detected correctly (NTSC)👍

 

The four consoles were:

• 2600 Atari Heavy Sixer - S/N 35401F
• 2600 Sears Tele-Games Light Sixer - S/N Missing
• 2600 Atari "Sunnyvale" Light Sixer - S/N 75655L
• 2600 Atari 4 Switch - S/N 81914252

[alex_79]

Autodetection never failed for me when running Draconian on my consoles, including my SECAM one.

[alex_79]

BTW, it would be nice if someone with an unmodified PAL-M (TV system used in Brazil) console could test this. It should be autodetected as NTSC (PAL-M consoles use the same palette as NTSC)

 

PAL-M has a slightly slower color clock compared to NTSC (3.575611 MHz VS 3.579575).

[ZeroPage Homebrew]

Draconian detects NTSC correctly every time on:

• NTSC Atari 2600 Jr. (Comp Mod): SN AT860024927
• NTSC Atari 2600 Light-Sixer (RGB Mod): SN 568407271

- James

[juansolo]

Got a RGB modded PAL six switch.

 

Draconian and Frantic both correctly select PAL

 

Interestingly the PALvsNTSC2 rom returns NTSC

Edited September 4, 2020 by juansolo