PC ORG @ 0x1e + ! ( chkPS )
    HL PUSHqq,
    RAMSTART LDHL(nn), ( RAM+00 == INITIAL_SP )
( We have the return address for this very call on the stack
  and protected registers. Let's compensate )
    HL DECss,
    HL DECss,
    HL DECss,
    HL DECss,
    SP SUBHLss,
    HL POPqq,
    CNC RETcc,      ( INITIAL_SP >= SP? good )
    JR, L2 BWR      ( abortUnderflow-B298 )