;==============================================================================
;  MSP430 Floating Point Package   Version 4.0 IAR
;
;  Conversion Subroutines
;  Texas Instruments Deutschland                IAR Version
;  Date:    January, 6 1997                     March, 14 2000
;  Author:  Lutz Bierl TID 4711
;  Version: 4.02                                4.03
;	    3.0   First version
;	    4.0   Comment enhancements and corrections
;
;============================================================================
;
;  This Conversion Package supports the following Integer Conversions:
;
;  CNV_BIN40   40 Bit binary to floating point		(24/40 mantissa)
;  CNV_BIN32U  32 Bit unsigned binary to floating point (24/40 mantissa)
;  CNV_BIN32   32 Bit signed binary to floating point	(24/40 mantissa)
;  CNV_BIN16U  16 Bit unsigned binary to floating point (24/40 mantissa)
;  CNV_BIN16   16 Bit signed binary to floating point	(24/40 mantissa)
;  CNV_BIN     40 Bit binary buffer to floating point	(24/40 mantissa)
;  CNV_FP_BIN  Floating point to binary 40 bits 	(24/40 mantissa)
;  CNV_BCD_FP  12 digit signed BCD  to floating point	(24/40 mantissa)
;  CNV_FP_BCD  FP number to signed 12 digit BCD number	(24/40 mantissa)
;
;  Errors are written to the Status Register SR: N = 0: no error
;						 N = 1: error occured
;
;  The conversion subroutines may be used for mantissas with 24 bits and
;  with 40 bits: the value of DOUBLE decides which length is used:
;  DOUBLE = 0:	24 bit mantissa (4 bytes per floating point number)
;  DOUBLE = 1:	40 bit mantissa (6 bytes per floating point number)
;
;  MSB=.31	   .23			  LSB=.0	   .FLOAT format
;  +-------------------------------------------+
;  | e.7 ... e.0 | sign | m.22 ........... m.0 |	   DOUBLE = 0
;  +--------------------.----------------------+
;   Exponent E	       DP     Mantissa M
;
;  MSB=.47	   .39				    LSB=.0 .DOUBLE format
;  +-----------------------------------------------------+
;  | e.7 ... e.0 | sign | m.38 ..................... m.0 | DOUBLE = 1
;  +--------------------.--------------------------------+
;   Exponent E	       DP     Mantissa M
;
;  Explanation of the FPP: see Metering Application Report
;============================================================================
;
;  For all Conversion Subroutines:
;
;  - Two (three) free words have to be allocated on the stack
;  - Arguments are not changed (except if on TOS)
;  - All pointers point to the MSB part of the numbers
;  - After the completion both pointers (and the SP) point to the result
;    on top of the stack (TOS)
;
;  Call Example (written for both formats):
;
;	CALL	  #FLT_SAV     ; Save registers
;	SUB	  #(ML/8)+1,SP ; Allocate stack for result
;	MOV	  #bcdb,RPARG  ; Load address of BCD-buffer to RPARG
;	CALL	  #CNV_BCD_FP  ; Convert BCD (or binary) number to FP
;	MOV	  #val3,RPARG  ; Load address of FP number to continue
;	CALL	  #FLT_xxx     ; Calculate next result
;	....	  ........     ; Continue until final result is calculated
;	CALL	  #CNV_FP_BCD  ; Convert final FP result to BCD
;	JN	  CNVERR       ; FP number too big for BCD buffer
;	POP	  bcdmsd       ; BCD number MSDs and sign
;	POP	  bcdmid       ; BCD digits MSD-4 to LSD+4
;	POP	  bcdlsd       ; BCD digits LSD+3 to LSD
;			       ; Stack is corrected by POPs
;	CALL	  #FLT_REC     ; Restore registers
;	....	  ........     ; Continue with program
;
;===========================================================================
; The flag SW_RND is defined in the user's program:
;
; SW_RND    EQU        0       ; 0: no rounding    1: rounding used
;
;   BEGIN OF THE FLOATING POINT CONVERSION SUBROUTINES
;
; Integer to Floating Point Conversions. A 3-word buffer is prepared and
; and converted. All conversions use this register buffer BIN_MSB to BIN_LSB.
;---------------------------------------------------------------------------
; 40 Bit binary to floating point (signed and unsigned). RPARG points to MSBs
; of a 3 word buffer. Range: -2^40+1 to +2^40-1 (-1.099x10^12 to +1.099x10^12)
; FF00 0000 0001 to 00FF FFFF FFFF
;
; Call    MOV   #BINMSB,RPARG   ; Pointer to MSBs of a 3 word number
;         CALL  #CNV_BIN40      ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN40 MOV    @R5+,BIN_MSB
	  JMP	 CNVL$1

;---------------------------------------------------------------------------
; 32 Bit binary to floating point (signed). RPARG points to MSBs
; of a 2 word buffer. Range: -2^31 to +2^31-1 (-2.14x10^9 to +2.14x10^9)
;
; Call    MOV   #BINMSB,RPARG   ; Pointer to MSBs of a 2 word number
;         CALL  #CNV_BIN32      ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN32 TST    0(R5)          ; Check sign
          JGE    CNV_BIN32U     ; Pos.: Use 32 bit unsigned conversion
          MOV    #0FFFFh,BIN_MSB ; Neg. number: set MSBs to FFFF
          JMP    CNVL$1
;
;---------------------------------------------------------------------------
; 32 Bit unsigned binary to floating point conversion. RPARG points to MSBs
; of a two word buffer. Rang e: 0...2^32-1
;
; Call    MOV   #BINMSB,RPARG   ; Pointer to MSBs of a 2 word number
;         CALL  #CNV_BIN32U     ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN32U CLR   BIN_MSB        ; High word is cleared
CNVL$1    MOV    @R5+,BIN_MID
          MOV    @R5,BIN_LSB
          JMP    CNV_BIN
;
;---------------------------------------------------------------------------
; 16 Bit binary to floating point (signed). RPARG points to value.
; Range: -2^15 to +2^15-1 (-32768 to +32767)
;
; Call    MOV   #BINMSB,RPARG   ; Pointer to MSBs of a 1 word number
;         CALL  #CNV_BIN16      ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN16 TST    0(R5)          ; Check sign
	  JGE	 CNV_BIN16U	; Use 16 bit unsigned conversion
          MOV    #0FFFFh,BIN_MID ; Neg. number: set MSBs to FFFF FFFF
          MOV    #0FFFFh,BIN_MSB
          JMP    CNVL$2
;
;---------------------------------------------------------------------------
; 16 Bit binary to floating point (unsigned). RPARG points to value.
; Range: 0 to +2^16-1 (0 to 65365)
;
; Call    MOV   #BINMSB,RPARG   ; Pointer to MSBs of a 1 word number
;         CALL  #CNV_BIN16U     ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN16U CLR	 BIN_MSB	; Set MSBs to zero
	  CLR	 BIN_MID
CNVL$2    MOV    @R5,BIN_LSB

;---------------------------------------------------------------------------
; 48-bit signed integer in BIN_MSB to BIN_LSB
; This call may be used if the 48-bit number is yet in BIN_MSB to BIN_LSB
;
; Call    MOV   binmsb,BIN_MSB  ; Load MSBs of a signed 48 bit binary number
;         MOV   binmid,BIN_MID  ;
;         MOV   binlsb,BIN_LSB  ; Load LSBs
;         CALL  #CNV_BIN        ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
CNV_BIN   MOV	 BIN_MSB,2(SP)	; Store MSBs with sign in result MSBs
          TST    BIN_MSB        ; Check sign of number
          JGE    NORM           ; Pos.: yet ok
          INV    BIN_LSB        ; Neg.: Absolute value needed
          INV    BIN_MID        ; Invert value of 3-word buffer
          INV    BIN_MSB
          INC    BIN_LSB        ; Complement 3-word buffer
          ADC    BIN_MID
          ADC    BIN_MSB
	  JMP	 NORM		; Go to common conversion part
;
;---------------------------------------------------------------------------
; BCD to Floating Point Conversion. A 3-word buffer containing a signed BCD-
; integer number is converted to a 32 bit or 48 bit floating point number.
; RPARG points to the MSD word of the buffer. The MSB of this word contains
; the sign: 0 = positive, 1 = negative
; Range: -8x10^11 + 1 to +8x10^11 - 1
;
; Call:   RPARG points to MSDs of BCD-Buffer  (sign in MSB of MSD)
; Return: RPARG, RPRES and SP point to result on TOS
;
; Call    MOV   #BCDbuffer,RPARG   ; Pointer to MSDs of a 3 word buffer
;         CALL  #CNV_BCD_FP     ; Call conversion routine
;         ...                   ; Result on TOS (2 or 3 words FP number)
;
;
CNV_BCD_FP EQU   $
          MOV    RPARG,RPRES    ; Copy pointer
          IF     DOUBLE=1
          MOV    @R11+,BCD_MSB  ; Sign, MSD to MSD-3
          MOV    @R11+,BCD_MID  ; MSD-4 to LSD+4
          MOV    @R11,BCD_LSB   ; LSD+3 to LSD
          ELSE
          MOV    @R9+,BCD_MSB   ; Sign, MSD to MSD-3
          MOV    @R9+,BCD_MID   ; MSD-4 to LSD+4
          MOV    @R9,BCD_LSB    ; LSDs
          ENDIF
          MOV    BCD_MSB,2(SP)  ; Store MSBs with sign in result space
          CLR    BIN_MSB        ; Clear binary buffer
          CLR    BIN_MID
          CLR    BIN_LSB
;
; BCD to Binary Conversion: 12 BCD-digits to 40 bit binary
;
	  MOV	 #12*4,COUNTER	; Digit counter x 4 bits
          BIC    #08000h,BCD_MSB     ; Clear sign bit
BCD_LOP1  RLA    BIN_LSB        ; MPY binary result with 10
          RLC    BIN_MID
          RLC    BIN_MSB
          PUSH   BIN_MSB        ; Store doubled value
          PUSH   BIN_MID
          PUSH   BIN_LSB
          RLA    BIN_LSB        ; x 4
          RLC    BIN_MID
          RLC    BIN_MSB
          RLA    BIN_LSB        ; x 8
          RLC    BIN_MID
          RLC    BIN_MSB
          ADD    @SP+,BIN_LSB   ; x(8 + 2)