DSKY flash period

[kuddel]

Hi there,

I like to know if anyone has a good source (apart from what I list here) about the flashing interval / period of the VERB NOUN Flash of the DSKY?

My findings (so far):

1. The flashing is done by the DSKY, not by the AGC.
   So the frequency is determined by a circuit in the DSKY (absolute accuracy is not that important here).
2. The document "APOLLO GUIDANCE AND NAVIGATION SYSTEM LUNAR MODULE STUDENT STUDY GUIDE"[1] (page 1-25)
   states : "[...]the VERB - NOUN display panels will flash on and off at a 1.5 cps rate[...]".
3. However the video "Apollo 11 - Unscheduled TV - 030:58:00 GET"[2]
   shows a quite long DSKY flashing sequence, which definitely shows that the period is not 1.5 cps!
   It looks more like a 1.5 second period (and a 1:3 OFF/ON duty cycle).

I know that the document references the Lunar Module in it's title, and the video shows the Command Module, but I think the DSKYs should be quite similar - or are they not?
The 1.5 cps would mean a 666.666 milliseconds period, but that seem to be much to fast.

Has anyone another source? Or possibly a link to schematics from which I might determine the frequency from?

Thanks in advance,
Kuddel

P.S.: I know that the document[1] has some typos all over the place, so I would not be surprised when the "1.5 cps" should have been "1.5 s period".

---
[1] https://www.ibiblio.org/apollo/hrst/archive/1709b.pdf
[2]

 

[kuddel]

Addendum:
In "ND-1021042, AC Electronics, "Lunar Excursion Module PGNCS Manual" Volume II (page 4-655) it seems to fit better:

[...]
If the VERB-NOUN combination punched in requires additional data to be furnished
by the operator, the VERB and NOUN displays flash once every 1.5 seconds after the
ENTR key has been pressed. The flashing indicates that the operator should punch-in
the required data on the keyboard. After punching in the required data and the ENTR
key, the flashing ceases.
[...]

and

[...]
The driver circuits and relays associated with signals UPLINK ACTY, OPR ERROR,
KEY REL, and STBY will apply, when activated, +5 volt status power to their respective
indicators on the DSKY front panel. Indicators OPR ERRand KEY REL flash at a 1.5 cps
[...]

Which seems to indicate that the VERB/-NOUN flash and the indicator lights flash had individual timings.

Note, that the document contains two pages 4-665! Both the quotes are from a 4-665 page, though

 

[ggalfi]

Hi there,

I like to know if anyone has a good source (apart from what I list here) about the flashing interval / period of the VERB NOUN Flash of the DSKY?

Hi,

Verb-Noun flashing is driven by the AGC. If you look at schematics page 16-2 at about tile 3D, you can see how this flashing signal VNFLSH for DSKY is generated by blending Bit6 of Channel 11 with another signal called FLASH. When VNFLSH (and also FLASH) is 1, that means for DSKY to turn off the Verb-Noun numbers. Generation of FLASH could be seen on page 24-2, tile 4F. It gives simply FLASH=not (FS16 or FS17), where FS16 and FS17 are the 16th and 17th bits of the Scaler, the internal timer of AGC. FS1 changes value in each 10/1.024 μs, so FS16 changes value in each 320ms. By definition of FLASH, V/N is turned off when both FS16 and FS17 are zero, and for other three combinations (01,10,11) it is turned on. So V/N is turned off for 320ms and turned on for 960 ms, having a cycle of total 1280ms ~ 1.3 sec.

 

[kuddel]

@ggalfi : Thank you very much for the detailed explanation ?
Especially the explanations about the AGC scaler - bits FS16 & FS17!
Most "overview documentation" I've come across briefly only state something like "[...]Flashing of VERB/NOUN is controlled by the VNFLSH signal (Channel 11 bit 6)[...]", which is not wrong, but lacked the details I would like to know.

Again, thanks a million!

Now I'll have to study the schematics and see if I can figure out whether the caution and warning lights that flash ("KEY REL" & "OP ERR") are derived from the scaler as well (I do believe now).

 

[ggalfi]

Again, thanks a million!

Bitte schön

Now I'll have to study the schematics and see if I can figure out whether the caution and warning lights that flash ("KEY REL" & "OP ERR") are derived from the scaler as well (I do believe now).

I don't want to take the joy of discovery away from you, so !!SPOILER AHEAD!!

Yes, they will blinking synchronously all together. On page 16-2 you can also see that signals for KYRLS and OPEROR are also fed from FLASH. You may also notice that in my previous post I was a bit sloppy as VNFLSH is actually using FLASH/ instead of FLASH. But FLASH/ is simply the negation of FLASH so ultimately VNFLSH=FLASH when Ch11B6 is 1. The reason behind KYRLS and OPEROR are built upon FLASH (unlike VNFLSH) is that these two are "turn on" signals, and VNFLSH is a "turn off" type.

 

[kuddel]

I'm not sure whether animated GIFs work here (should repeat only 3 times), but here's what I think the flashing should look like, right?

The sequence you see:

1. RSET (to clear my 'initial' program alarm)
2. V35 (Test Lights - to demonstrate the FLASH vs. FLASH/)
3. V36 (Just to clear the display and lights...)
4. V37E00E (Change Major Mode - to IDLE "goto Poo" - just to seen the VNFLSH flash a little longer)

The absolute phase of the flashing (in relation to transitions of scalar bits) is not that important for my simulation

I hope that this behaviour is not too far off

Again, thank you very much (also for the spoiler ?)

 

[ggalfi]

I hope that this behaviour is not too far off

Let's say, it is close to be perfect, just having some minor glitches

First of all, OPRERR, KEYREL and V/N are flashing absolutely unisonly: with the same profile and phase. Despite the signals are going like this:

VNFLSH: 100010001000
KYRLS:  011101110111
OPEROR: 011101110111

the actual lights on DSKY will go like this:

V/N lights:   Dark - Light - Light - Light - Dark - Light - Light - Light - Dark - Light - Light - Light
OPRERR light: Dark - Light - Light - Light - Dark - Light - Light - Light - Dark - Light - Light - Light
KEYREL light: Dark - Light - Light - Light - Dark - Light - Light - Light - Dark - Light - Light - Light

, because the DSKY interprets VNFLSH in an oposite way as it does for KYRLS and OPEROR signals. The reason - I guess - is the default setting for these lights: the Verb and Noun numbers are turned on, the warning lights are turned off by default.

Secondly, when you run V35, RESTART and STBY lights will be turned on as well. If you look at the code for V35, you may see that at some point it sets Channel13 Bit10 to "1". This will turn on ALTEST signal (see page 23-2, tile 3B) which is fed into Standby and Restart circuitry (see page 18-1 6A and page 13-1 3B, respectively), so eventually turning up these lights as well.

Thirdly, this applies only if the DSKY state what you are showing on this animation is right after the (re)start of AGC: the Restart circuitry guarantees that if AGC is restarted (technically went into GOJAM state), then it will turn on the RESTART light as well. So in a real restart situation this light isn't software, rather hardware driven. Also having a program alarm (as far as I remember, 1107) on start is due to some minor bug in VirtualAGC. So if you aren't using VirtualAGC behind your DSKY, you don't have to turn on PROG light to achieve historical accuracy.

 

[kuddel]

Yes, I am using -a very old version though- of VirtualAGC converted into JavaScript ages ago
The DSKY is just the DSKY, trying to render channels 8, 9 & 11 (010, 011 & 013 octal) and providing signals to channel 13 & 26 (015 & 032 octal).
So the actual behavior of the AGC is 'kind of' out of my hands.
Nevertheless I can make the lights and VERB NOUN flash "in phase" to get to my desired "realism" ?

Again thank you for looking closely into this, it's very very educational!

 

[kuddel]

So now it looks like this:


I have re-uploaded the 1st animated gif to make clear that it's wrong

Next I might change the drawing of the 7 segment display to be 2more accurate". My current implementation uses "modern 7 segment" drawing on canvas, which I might change to render it more accurate (using this web-font possibly)