Some users of SpaceWire can be confused about The Standard’s document number within the European Cooperation for Space Standardization (ECSS). The ECSS publishes standards for ESA contractors to follow, with a view to improving standardisation within the space sector. In February 2003, the ECSS published The SpaceWire Standard under the documentation number ECSS-E-50-12A. However, in July 2008 The SpaceWire Standard was re-numbered to ECSS-ST-E-50-12C. This led to technical papers, marketing material, and general information about SpaceWire referring to two different documentation numbers.
In short, there are no differences between ECSS-E-50-12A and ECSS-ST-E-50-12C. Both documents include the same technical content and only reason for the change was to ensure The Standard fitted in with the new ECSS numbering system. Therefore any information relating to the ‘old’ ECSS-E-50-12A is still applicable to The SpaceWire Standard, although the newer ECSS-ST-E-50-12C is now much more commonplace.
Those using the RMAP protocol (you can learn about it here) may also have encountered the documentation number ECSS-E-ST-52C. This document outlines the technical details of the higher level protocol which works over SpaceWire.