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Ian Wigglesworth
750 Posts
Hope someone can help with this!

I have this CT elektronic decoder fitted to a diesel 04 shunter and it's being a swine!

It says that programming CV1 with a value of 0 gives it a hardreset.

So I did that first.

Set a short address to 7

Ran the loco all ok works fine, but very slow at top speed.
So I altered CV5 (Max speed top volts) to a value of 200, it says the range is 0-255.

I couldn't then run the loco as the address had changed to 200!

This seems to happen no matter what settings I put in, when ever I change any of the speed settings the address changes as well!
This decoder was replaced only a week ago, and I've only just got round to running it, now find it's playing up, is it another decoder required?


Ian Wigglesworth
750 Posts
Discussion Starter · #2 ·
This is mental!

Carried out a decoder reset and also went through decoder recovery program with the PowerCab.

If I program CV1 (short address) with a value of 7 then select loco 7, the loco will run forwards and in reverse but very slow.

So go to CV5 and that is reading 7 ?? So I enter 250 which is almost top volts and the address in CV1 now reads 250

It doesn't seem to effect the long address, but somethings not quite right.

Very very strange, me thinks the decoder is having a brain drain!

Any other ideas anyone?

Ian Wigglesworth
750 Posts

I can't be 100% sure, as I tried lots of different things but I do believe that is whats happening.
As when I program CV1 short address to say 7
Then CV5 and CV6 read the same as CV1 thats a fact, didn't check the others but I can do later.
As for paged mode I'm not sure, just use program track on the PowerCab, which I assume would default to page mode?

Is there any way round this, if this is actually the case.

Ian Wigglesworth
750 Posts
Well it works, but only in DIRECT MODE!!

Luckily, Mike Bolton from MERG had just sent an email regarding a new PIC program for the Standalone programmer! Excellent timing!

This new program was for some problematic sound decoders, but it has also meant the MERG standalone programmer will now read and write CV's in DIRECT mode on the CT Elektronic decoders.

The programmer already had Direct mode programming but wouldn't work with the CT Elektronic decoder, this little bit of information from Mike may help.

Maybe I can explain a bit about 'direct mode' programming. When reading in
direct mode, you ask the decoder is bit 'n' a one or a zero by sending it
the bit and asking it to 'verify' it. If it is the same as the one you sent
you get an ACK, if it is not, you get NO ACK. To speed things up with the
original MERG programmer code, we just sent ones and if there was no ACK we
assumed it must have been a zero. This meant only sending 8 bits to verify.
However, as a check we then did a direct 'byte' read which should confirm
the value with an ACK. The NMRA RP does say that a decoder that supports
direct mode should support both bit and byte read / write. Unfortunately
not all manufacturers have conformed to this. Some, like CT only do the bit
mode so will fail to verify with a byte read. Some, I believe only do the
byte read.

For the direct mode programming we only implement the byte write. Hence the
CT would program but not confirm it.

As the CT decoder is 'non compliant' it failed when using the strict RP
interpretation but still actually programmed. We also had problems with some
other decoders where the delay between the ACK and trying to read the next
bit was too short. The RP says 'one or more' reset packets needed. In the
latest code we included more reset packets and also changed the bit read
sequence so it checks for both a one and a zero (needs 16 tries instead of
8) but now we assumed the read would be correct so dropped the byte verify
as confirmation. This should now work with the CT decoders. The added resets
also enabled a Digitrax decoder to work in direct mode and some sound
decoders which were problematical. All but the QSI ones will now read in
direct mode. QSI still needs the page mode. The additions do make the
direct read a bit slower.

So thanks to Mike Bolton for the explanation!
Hope others find it useful.

CT decoders are great in that they are so very small, and will fit where you would never believe possible,but they do need quite a bit of playing with to get the motors to run well.
They are not a great 'out of the box' decoder!
The instructions are a bit rubbish and hard to follow as well.
Once you have them set up though they do perform very well and the slow speed you can get is incredible!

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