Re-program 10 Trains at Once?

[Sir TophamHatt]

Just double checking.

 

If I need to re-program a couple of CV values to about 10 locos at once, can I just stick them all on the main track and do it at the same time?

 

Surely the controller won't care what trains are on the track and just send the new CV value to whatever is on the track at that point?

 

Cheerio

[Crosland]

You can't use "on the main" or "ops mode" programming to program multiple locos at once.

 

You would need to connect the programming track output to your main track and ensure ONLY the locos you want to reprogram are on the track.

 

Worst I can see happening is (a) the controller doesn't like the extra load or (b) some locos don't program correctly as another one acknowledges too soon and curtails the programming operation.

 

The technique is sometimes used to program function only decoders in multiple units, using the decoder that's connected to the motor to control the acknowledgement. I've not actually heard of (b) happening in that scenario.

[fcwilt]

Just double checking.

 

If I need to re-program a couple of CV values to about 10 locos at once, can I just stick them all on the main track and do it at the same time?

 

Surely the controller won't care what trains are on the track and just send the new CV value to whatever is on the track at that point?

 

Cheerio

 

Using the "programming track" means the command station will try to read back the value of the CV being programmed. You can imagine what might happen with multiple locos responding at the same time.

 

Using "programming on the main" requires specifying the address of the loco to change - so naturally you cannot change multiple locos at one time.

 

Frederick

[Nigelcliffe]

Both replies (Andrew and Frederick) are accurate,  BUT,  there are a number of systems on sale from a variety of manufacturers which put the programming output and track output on the same terminals, and rely on internal switching between which mode is in use.  

 

Those can, potentially, write program everything on a layout in one hit.    The can't read multiple items (as Frederick says, the read result would be garbage), but they can write.   

 

 

 

- Nigel

[Oldddudders]

Just double checking.

 

If I need to re-program a couple of CV values to about 10 locos at once, can I just stick them all on the main track and do it at the same time?

 

Surely the controller won't care what trains are on the track and just send the new CV value to whatever is on the track at that point?

 

Cheerio

 

You haven't understood POM - Programming On The Main - at all. It is only available for one loco at a time - and rightly so. It is immensely useful for amending the settings on CVs for a loco as it runs - be it sound settings, or acceleration/deceleration etc . It enables the user to monitor and adjust by trial and error very easily. Check your commadnd station literature for how it works with your system. 

[bgman]

Or possibly

 

 

D.O.N. Tryit

[michaelp]

Could mean a lot of work if it goes wrong

[RAF96]

As stated there are systems whereby the programming output goes out on the same terminals as the main. Some of these systems will program at full current not NMRA reduced and interrupted current, so it is possible to affect all locos on track by sending a reset, but also as stated POM requests the current (sorry) address of the decoder you are going to change so it is inherantly safe from broadcast fleetwide programming errors.

Rob

[Crosland]

Using the "programming track" means the command station will try to read back the value of the CV being programmed. You can imagine what might happen with multiple locos responding at the same time.

 

This is what I alluded to with the acknowledge timing being different between decoders. You will either get a successful read or a garbled value.

 

If the combined acknowledge current pulses from all the decoders is too great this would be noticed during the (attempted) write.

[Sir TophamHatt]

And advice like this is why I hate just "trying it and see".

One at a time then!

Thank you all

[fcwilt]

This is what I alluded to with the acknowledge timing being different between decoders. You will either get a successful read or a garbled value.

 

If the combined acknowledge current pulses from all the decoders is too great this would be noticed during the (attempted) write.

 

And then you have those cases, like CV29, where the command station has to read the current value in order to change one or more bits while leaving others alone.

 

That could be fun. 

 

Frederick

[WIMorrison]

Why do you need to read CV29 when you don’t need to read the other CVs?

 

If you want to write 13 to CV29 then you simply write it, same as you write13 to CV3 if that is what you want it to be.

 

CV29 is no different to any other CV.

[fcwilt]

Why do you need to read CV29 when you don’t need to read the other CVs?

 

If you want to write 13 to CV29 then you simply write it, same as you write13 to CV3 if that is what you want it to be.

 

CV29 is no different to any other CV.

 

Hi,

 

Consider CV1 - it contains one value - the short address. If you wish to change the short address to, say, 55, you have only to program CV1 to 55 and you are done.

 

CV29 on the other hand is perhaps the most common CV that gets changed which contains multiple, independent pieces of information. For instance bit 5 is set to one to use the long address, bit 4 is set to one to enable the use of the speed table. 

 

If you wish to enable using a long address yet leave the other bits alone you need to read the current value in CV29, set bit 5 of that value to a one and then write that updated value back to CV29.

 

Certainly if you know what values you wish to set for each of the possible bits you can just write CV29.

 

But the programming tools I have used all read CV29 first when changing it.

 

YMMV.

 

Frederick

[WIMorrison]

If you want to enable railcom, set dc operation and reverse the loco direction you simply send 13 to CV29, how it is set now is immaterial, it will be 13 afterwards

 

If you want to read CV29 then you need Railcom if you want to POM or place the loco on a programming track.

 

It is the same as any other CV, work out what you need it to be and send the value to the decoder. If you don’t know the value before hand then you have the same problem that you have with any value you don’t know, you either read it or better, work out what it needs to be and send the value to the right CV

Edited March 2, 2018 by WIMorrison

[fcwilt]

If you want to enable railcom, set dc operation and reverse the loco direction you simply send 13 to CV29, how it is set now is immaterial, it will be 13 afterwards

 

If you want to read CV29 then you need Railcom if you want to POM or place the loco on a programming track.

 

It is the same as any other CV, work out what you need it to be and send the value to the decoder. If you don’t know the value before hand then you have the same problem that you have with any value you don’t know, you either read it or better, work out what it needs to be and send the value to the right CV

 

You don't need to know the value of the short address in CV1 if you simply want to change it. 

 

You DO need to know the value in CV29 if you wish, say, to to start using the Speed Table but leave everything else alone.

 

As I said IF you know in advance the desired value of every bit in CV29 you could just write it.

 

There is a fundamental difference between CVs that contain just one piece of information and those that contain multiple pieces of information.

 

Frederick

[WIMorrison]

Your argument applies to any cv, if you need to know how it is set then you need to read it - cv29 is not a special case, in fact it is simpler as there are only 8 switches that can be either on or off, that is all it can do.

 

And you should be programming cvs based upon what you want them to do, ergo simply work out what it should be - or any other cv should be set at, then write it.

 

Nothing special mystical or magical about cv29, want to use a complex speed curve as well as the other options above? Thenmake the value 29 - though that may confuse someone reading the cv as they may think it is the cv number

[fcwilt]

I give up. You are missing the point.