collapseos/blk/290

lblchkPS BSET ( chkPS )
    ( thread carefully in there: sometimes, we're in the
      middle of a EXX to protect BC. BC must never be touched
      here. )
    EXX,
( We have the return address for this very call on the stack
  and protected registers. 2- is to compensate that. )
    HL PS_ADDR 2- LDdi,
    SP SUBHLd,
    EXX,
    CNC RETc, ( PS_ADDR >= SP? good )
    ( continue to uflw )
lbluflw BSET ( abortUnderflow )
    DE BIN( @ 0x06 ( uflw ) + LDd(i),
    JR, lblexec BWR