Parameters for postmortem debugging can be saved by intercepting _fp_trapveneer(). The $Super$$ and $Sub$$ mechanism can be used to intervene in all calls to _fp_trapveneer(). For example:

    AREA foo, CODE
IMPORT |$Super$$_fp_trapveneer|
EXPORT |$Sub$$_fp_trapveneer|
    |$Sub$$_fp_trapveneer|
;; Add code to save whatever registers you require here
;; Take care not to corrupt any needed registers
    B |$Super$$_fp_trapveneer|
    END