I am looking through NMRA S9.2 speed and function commands. I see the packet structure for one byte address, but I don't see the structure for longer address packet structure.
I am also looking for the 128 speed-step packet structure. I gather it might be an extra byte appended to the 28 speed-step command (for backwards compatibility) but I would like to see the documentation for that packet structure. Could someone please direct me to the correct line/document for long address control commands and 128 step speed commands?
It's all explained in 9.2.1. Section C is the address. Paragraph around line 70 explains how it works - if the first bits of the address are 11 and the remaining bits are not 111111, then a second address byte must immediately follow. This is when the first address byte is 11000000 to 11100111. 2 bits not available to use - so extended addresses are only 14 bits, not a full 16.
Speed control starts around line 200.
Are you looking at the standards from this page:
https://nmra.org/index-nmra-standards-and-recommended-practices
You can clearly see the additional information laid out below the main standard. In this case, 9.2.1 for extended packet formats - the stuff added after the basic standard, which only had single byte addresses and 14 speed steps. Everything beyond that is extended packet formats.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks again Randy.