; Divide

;       UM/MOD  ( udl udh un -- ur uq )
;       Unsigned divide of a double by a
;       single. Return mod and quotient.

        HEADER  UMMOD "UM/MOD"
UMMOD:
        PUSHW   X               ; save stack pointer
        LDW     X,(X)           ; un
        LDW     YTEMP,X         ; save un
        LDW     Y,(1,SP)        ; X stack pointer
        LDW     Y,(4,Y)         ; Y=udl
        LDW     X,(1,SP)        ; X
        LDW     X,(2,X)         ; X=udh
        CPW     X,YTEMP
        JRULE   MMSM1           ; X is still on the R-stack
        POPW    X
        INCW    X               ; pop off 1 level
        INCW    X               ; ADDW   X,#2
        LDW     Y,#0xFFFF
        LDW     (X),Y
        CLRW    Y
        LDW     (2,X),Y
        RET
MMSM1:
        LD      A,#17           ; loop count
MMSM3:
        CPW     X,YTEMP         ; compare udh to un
        JRULT   MMSM4           ; can't subtract
MMSMa:
        SUBW    X,YTEMP         ; can subtract
        RCF
MMSM4:
        CCF                     ; quotient bit
        RLCW    Y               ; rotate into quotient
        RLCW    X               ; rotate into remainder
        DEC     A               ; repeat
        JREQ    MMSMb           ; if A == 0
        JRC     MMSMa           ; if carry out of rotate
        JRA     MMSM3           ; 
MMSMb:
        SRAW    X
        LDW     YTEMP,X         ; done, save remainder
        POPW    X
        INCW    X               ; drop
        INCW    X               ; ADDW   X,#2
        LDW     (X),Y
        LDW     Y,YTEMP         ; save quotient
        LDW     (2,X),Y
        RET