There are a few different combinations here and what you need to do depends on the combination.
Quick technical explanation:
LGB decoder control:
- "Parallel" mode is standard DCC control. DCC controller tells the loco to "Set a F-register to on/off" (e.g. "Set F3 to on"). Registers go from F0 (lights) to up to F8 or F16 or even F28 or so, depending on how many your decoder supports.
- "Serial" mode is an LGB hack. Rather than use F2..F8, the controller toggles F1 some number of times. Typically, this toggles F{x}, where x = number of times F1 toggled. Rate of F1 toggling is about 1 per second, with a longer gap indicating the end of the sequence.
Your decoder will almost certainly support proper "parallel" operation. Some controllers support "serial" (or "F1 pulse", which is a better name) mode. Unless you need to interoperate with very old LGB control systems (MTS I or II), just use standard ("parallel") mode and be done with it.
Where all this becomes more complex is once we start dealing with LGB sound boards. With many of the old locos, F0 controlled the lights and everything else was controlled via the sound board, implemented by piping F1 directly to A1 (the sound board interface). So now there is a truly "serial" connection between the decoder and the sound board. Actually, it usually ends up as a serial connection between the
controller and the sound board, proxied by the decoder (which just toggles A1 to match F1).
There are a few options to drive these sound boards:
- If your controller supports "F1 pulse", then you can set this mode for this loco and the controller will convert F1-F8 into an appropriate number of pulses, which will then toggle F1 on the decoder and thus toggle A1 for the sound board to read. This works fine as long as you have a controller that supports it and make sure you don't use F1-F8 to drive any actual outputs on the decoder.
- Trick: in this case, you are better to set the decoder to "parallel" mode and just let it proxy F1 to A1. If you need to drive A2 or other functions just make sure you set them to be driven by F9 or above.
- If you don't mind pain, you can manually toggle F1 on the handset (and count the pulse and make sure you toggle it about every 0.75 seconds). It should also be possible to script this behaviour, if you can find a handset to support it.
- Finally, some decoders offer an option that can convert signals F1 to F8 into toggles of A1. This allows you to use a standard handset and the decoder maps regular F1..F8 commands into the A1 pulse / "LGB fast pulse" behaviour. But see below.
Decoder support for A1 pulse emulation:
- Massoth decoders designed to fit into the LGB 55020/55021 pins (eg eMotion L) offer "fast pulse" mode. This toggles A1 very quickly (less than 0.25s), while some of the older sound boards (e.g. LGB 28002) require a toggle rate much closer to 1 second. Also, the eMotion series have an odd "feature" where you can't enable A1 pulse without also enabling serial mode emulation (translate multiple incoming pulses of F1 to F1-F8).
- On my DRIVE-L, I need to make sure I don't toggle F1-F8 again why the decoder is processing the first request or the second signal is lost.
- Zimo MX large scale decoders offer "pulse chain recognition" (CV 112, bit 4) and "pulse chain generation" (CV 112, bit 7). Pulse chain generation is what you want, but I couldn't get an answer out of Zimo tech support about the pulse rate. The newer MS series are not documented as supporting either form of LGB pulse chain.
Conclusion
Options:
- Use a standard decoder and a controller that supports "serial" mode
- Use a decoder that supports "A1 pulse" mode and figure out how to configure it correctly for your sound board.
- Rip out the LGB electronics and replace them with a standard sound decoder setup.
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