Maybe its better to post thios question in the PSoC1 forums. In the PSoC5 world assembler is rarely used...
You are here in the PSoC5 forum, Designer 5.4 is for PSoC1 only.
In Designer -> help - > Documentation you find a C- manual and an Assembler manual. There you find the informations on how to interface both worlds.
Thank you all for the replies. I will be cross-posting this to the PSoC1 forums.