Will an r8247 work with a roco z21

[Hipwell]

My dad is after an accessory decoder to go with his z21 for operating points and I've suggested an r8247 as I use one with my select and e link and it works fine.

Is there any reason the Hornby one won't work with a z21? The manual only gives programming instructions for use with hornby controllers

[P-Henny]

Outside the Hornby brand, virtually all (or at least many) Acc Decoders are programmed using 'self learning' techniques which is pure simplicity. Hornby took another route completely, based upon writing CV's. Thus the answer to your question is totally reliant upon the capability of the controller being used (in your case Z21). The DCC specification defines the DCC packet formats, and the specification defines the programming packets for locos as being different to programming packets that are being used to programme Acc Decoders. Thus, just because any particular controller can programme a loco, does not automatically mean that it can also programme an Acc Decoder. In the case of the Z21, it may be able to programme a Hornby R8247, but then on the other hand it may not. One would need to read the Z21 manual at the very least. Of course, you could try the Z21 with one of your own R8247s first to try. If that is not convenient, then I would purchase another brand of decoder that is 'self learning' to minimise the risk of buying a R8247 that won't programme with the Z21. Programming a R8247 using non-Hornby kit may have issues as the R8247 is typically (but not exclusively) programmed using "Group Addressing" which may not be supported by non-Hornby controllers.

There shouldn't be any issue operating a R8247 with a Z21, once the R8247 is programmed. As operating an Acc Decoder, is using a DCC packet format definition that should be followed by all brands of controller.

[Hipwell]

Thanks for your reply Henry.

I have read the manual for the z21 but I'm still not confident how it will work really, it mentions that the z21 uses accessory addresses rather than loco address which I couldn't really get my head around as I thought a dcc address was a dcc address, so assumed that on the z21 if I select point 61 as I do on my select, then it would operate the point.

On my select and on railmaster with e link I just choose address 61 and it operates my point, railmaster, I just set the points on the virtual layout to the same address as I did on the select so it all works fine and I can change between select and e link depending on how I'm feeling!

I'll get him to bring his z21 round and see if we can work out how to get it going before he orders anything.

[P-Henny]

DCC Loco address packets have a different format to DCC Acc Decoder address packets (this statement is valid for all DCC brands and products, it is part of the NMRA DCC Specification to which all manufacturers should adhere). With the Select, DCC Addresses in the 1-59 range are automatically constructed by the Select as a Loco packet and DCC Addresses in the 61 to 99 range are automatically constructed in an Acc Decoder packet format. This is the reason why you can not have a Loco with an address above 59 when using a Select controller.

When using a Hornby Elite or Railmaster, then you have to manually tell the controller what packet format to use, hence why the Elite has both a Loco and ACC button that needs to be pressed as part of using an address. In Railmaster, the software knows what packet format to use (Loco or Acc) because these are manually configured as part of the software Loco and Accessory setting up in either the Loco or Accessory configuration screens.

[96RAF]

Just to add to that - Group Addressing is the standard, noticeable in that you can manually write (using say an Elite) a port address and the controller will translate the binary command to that group as required. Reading back an address will only show the group address.

For instance if you write a port address from 5 to 8 then group 2 will be the read back, write 9 to 12 and read back 3, etc in groups of four.

All this is explained in great detail in the R8247 version 2 manual. Vers 2.0 being a totally different beast to the older V1.0.

I would agree without breaking forum rules by recommending any particular make or model that choosing a self learning acc decoder is a more sensible option.

[Hipwell]

Ah right I see, so that's why In railmaster I can use an address of 1 for the accessories and 1 for a loco and the 2 don't get confused with each other.

The manual for the z21 multimaus doesn't really go in any depth of how to explain that.

So I'm wondering if I just select accessory number 61 in the z21 will it work or not. I suppose only testing will tell.

But as I say, with it set to 61 62 63 64, I can control them with my select or with railmaster no problem, so hopefully the z21 will do the same.

[P-Henny]

As I stated in a previous reply. There should be no issue operating a R8247 using a Z21, once the R8247 has been configured with an address.

Note that the R8247 brand new out of the box will have DCC address 1 to 4 for the four ports. Thus if only one R8247 is required then programming it should not be a requirement for operating Solenoid point motors. The Z21 would just use the factory default Accessory addresses 1 to 4 to operate the decoder.

It is just the ability of the Z21 to change the addresses on the R8247 to something different (i.e 5 to 8) that is in question.

There are Z21 'users' on this forum. They may be able to offer a more definitive 'yah nay' answer to this question.

[Fishmanoz]

There’s no rhyme or reason to start at address 61. This is a starting accessory decoder address for the Select only, doesn’t apply to any other controller (to my knowledge). With most/all other controllers, you start at accessory address 1, which is also the 8247 Port 1 starting address out of the box.

Personally, I’d avoid this whole programming business by using another brand with self learning. Instead of having to program them on the programming track, you install them on the track bus, move a switch on the decoder to learning (or bridge a pair of contacts) and the decoder remembers the address you send to it by operating a point at that address on your controller. Switch the learning switch back to run, and your done.

It’s been discussed here previously why, when Hornby updated their very old original 8247 design a couple of years back, they didn’t go to a self-learning design. For me, the only reason anyone buys these now is they say Hornby on the box, it’s not because they are better or cheaper than other designs.

[BigNoj]

I have a drawer full of R8247’s that no longer work may I suggest that you consider the Train-tech PC2 or the Digikeijs DR4018.

[Hipwell]

Thanks guys.

Well, we tested it with one of mine but for some reason with the z21 the numbers are all 4 in front.

So if I set the Hornby decoder to 1 2 3 4, in the z21 to activate them you have to choose accessory 5 6 7 8.

Any ideas why?

[Rog RJ]

I believe there is an option in the z21 software to cancel the offset.

The offset occurs because different companies treat bit zero differently due to a poor specification in the DCC standard.

Edit to add

Some number the eight bits 0 - 7 and others 1 - 8

[Hipwell]

Thank rog ill take a look in the z21 manual