The second DVB master mode is DVB-SNP, (looks like CHn in Cyrillic) which is the track-while-fly automatic engagement mode, the early Russian version of track-while-scan. In FC, you have to be in the PPS or ZPS “Scan” submodes to access SNP master mode.
Now, as I stated above, the interleaved-scan submode is abbreviated in-game “AVT,” or “af-to,” in Cyrillic. In other words, “Auto.” You may have read that this submode should be linked to the “automatic” tracking function of the track-while-fly SNP master mode rather than the PPS or ZPS submodes. In “Easy Tartar’s” review of the MiG-29’s radar here, he indicates this to be the case. I think Eagle’s got it right and “Auto” mode is correctly modeled. I got the scoop from none other than Oleg Tishenko-Eagle’s avionics genius. Be sure: how can ya go wrong on a technical flight sim question with a guy named Oleg? Anyway, Oleg’s point is that the for-real MiG-29 manual (how cool is that, readers?) they’re using at Eagle to model this functionality has “Auto” submode as the only one of DVB-Scan’s submodes that can’t enter SNP master mode. Look below for the reason why this is. 
And this would mean that the “Auto” in the title of Auto submode refers to the automatic switching from high to medium PRF and back again as the radar scans, rather than a link to SNP mode. Oleg sent me this interesting tidbit, via Matt Wagner, on how actual MiG-29 and Su-27 pilots get into SNP mode:
In real life, the TWS on Russian aircraft works in this manner:
MiG-29
TWS can be engaged ONLY if you was set radar to V (VSTRETCHA – closing to target) or D (DOGON – pursuit of target) by rotary “radar mode switch” and if you set “ZPS-PPS” switch (note it is another switch) to ZPS (ZADNYAYA POLUSHPERA – rear hemishpere), or to PPS (PEREDNYAYA POLUSHPERA – front hemishpere). These two switches must be correlated between each other. “D” corresponds to “ZPS”, and “V” corresponds to “PPS”. Overwise TWS-mode will not be engaged.About PFR. PFR – Pulse Frequency Rate. “V” corresponds to high PFR, and
“D” to medium PFR. In the AVT (AUTO) radar mode there is interleaved PFR. Interleaved PFR it is when frequency rate is switched between high and medium rates at each radar antenna scan period. This is the reason why TWS can not be engaged in AVT (AUTO) radar mode.Su-27
At Su-27 the “PPS-AVT-ZPS” switch toggles both PFR and ability to engage TWS mode. In AVT position you can not to engage TWS respectively.
This little piece of radar trivia aside, which I’m sure hardcore simmers will ENDLESSLY and joyfully debate on our boards, what DVB-SNP master mode does is prioritize targets for you. It will place the target designator box over the target with highest closing velocity, thus bugging it for you automatically, and track it without locking on until you’re in optimal engagement range for your selected weapon. However, unlike an American track-while-scan setup (cf. the F-15C’s APG-63), you don’t get Vc or aspect info on the bugged target. And since this is an early radar, you only have the ability to mark one target for termination. Once you’re in launch parameters for the selected ordnance, the system will automatically go into Attack (single-target-track) mode and ready a missile for firing. Post-1989 or so radars, like that found in later Su-27SMK aircraft, can prioritize and guide RVV-AE missiles to two targets, more like an American TWS setup can do with AMRAAM.
