anchor.diff:        (defun ,(intern "NSF-OUTPUT-FILE" package) (filename)
           (generate-nsf-preview ,name #',asm-fn-name :filename filename)))))
   
  -(defun emit-fixed-cycle-player (context var-base)
  +(defun emit-fixed-cycle-player (context var-base &key break-at-end)
     "Emit fixed-cycle player routine. Requires VAR-BASE specifies 8 bytes of adjacent zeropage storage."
     (check-type var-base (integer 0 250))
     (let* ((*context* context)
  
positive.code:         (lda mptr-msb)
          (cmp (zp (1+ endptr)))
          (asif :equal
            (when t ;;break-at-end, FIXME/TODO
              (brk)
               (db #xF1)
               (rts))
            (poke (zp startptr) mptr-lsb)
            (poke (zp (1+ startptr)) mptr-msb)))
  
        (rts))
  
  
negative.code: 
      (setf *origin* #x8000)
  
      (emit-fixed-cycle-player *context* #x80 :break-at-end break-at-end)
  
      (procedure init
        (cld)
  