path: root/arch/m68k/fpsp040/bindec.S

|
|	bindec.sa 3.4 1/3/91
|
|	bindec
|
|	Description:
|		Converts an input in extended precision format
|		to bcd format.
|
|	Input:
|		a0 points to the input extended precision value
|		value in memory; d0 contains the k-factor sign-extended
|		to 32-bits.  The input may be either normalized,
|		unnormalized, or denormalized.
|
|	Output:	result in the FP_SCR1 space on the stack.
|
|	Saves and Modifies: D2-D7,A2,FP2
|
|	Algorithm:
|
|	A1.	Set RM and size ext;  Set SIGMA = sign of input.
|		The k-factor is saved for use in d7. Clear the
|		BINDEC_FLG for separating normalized/denormalized
|		input.  If input is unnormalized or denormalized,
|		normalize it.
|
|	A2.	Set X = abs(input).
|
|	A3.	Compute ILOG.
|		ILOG is the log base 10 of the input value.  It is
|		approximated by adding e + 0.f when the original
|		value is viewed as 2^^e * 1.f in extended precision.
|		This value is stored in d6.
|
|	A4.	Clr INEX bit.
|		The operation in A3 above may have set INEX2.
|
|	A5.	Set ICTR = 0;
|		ICTR is a flag used in A13.  It must be set before the
|		loop entry A6.
|
|	A6.	Calculate LEN.
|		LEN is the number of digits to be displayed.  The
|		k-factor can dictate either the total number of digits,
|		if it is a positive number, or the number of digits
|		after the decimal point which are to be included as
|		significant.  See the 68882 manual for examples.
|		If LEN is computed to be greater than 17, set OPERR in
|		USER_FPSR.  LEN is stored in d4.
|
|	A7.	Calculate SCALE.
|		SCALE is equal to 10^ISCALE, where ISCALE is the number
|		of decimal places needed to insure LEN integer digits
|		in the output before conversion to bcd. LAMBDA is the
|		sign of ISCALE, used in A9. Fp1 contains
|		10^^(abs(ISCALE)) using a rounding mode which is a
|		function of the original rounding mode and the signs
|		of ISCALE and X.  A table is given in the code.
|
|	A8.	Clr INEX; Force RZ.
|		The operation in A3 above may have set INEX2.
|		RZ mode is forced for the scaling operation to insure
|		only one rounding error.  The grs bits are collected in
|		the INEX flag for use in A10.
|
|	A9.	Scale X -> Y.
|		The mantissa is scaled to the desired number of
|		significant digits.  The excess digits are collected
|		in INEX2.
|
|	A10.	Or in INEX.
|		If INEX is set, round error occurred.  This is
|		compensated for by 'or-ing' in the INEX2 flag to
|		the lsb of Y.
|
|	A11.	Restore original FPCR; set size ext.
|		Perform FINT operation in the user's rounding mode.
|		Keep the size to extended.
|
|	A12.	Calculate YINT = FINT(Y) according to user's rounding
|		mode.  The FPSP routine sintd0 is used.  The output
|		is in fp0.
|
|	A13.	Check for LEN digits.
|		If the int operation results in more than LEN digits,
|		or less than LEN -1 digits, adjust ILOG and repeat from
|		A6.  This test occurs only on the first pass.  If the
|		result is exactly 10^LEN, decrement ILOG and divide
|		the mantissa by 10.
|
|	A14.	Convert the mantissa to bcd.
|		The binstr routine is used to convert the LEN digit
|		mantissa to bcd in memory.  The input to binstr is
|		to be a fraction; i.e. (mantissa)/10^LEN and adjusted
|		such that the decimal point is to the left of bit 63.
|		The bcd digits are stored in the correct position in
|		the final string area in memory.
|
|	A15.	Convert the exponent to bcd.
|		As in A14 above, the exp is converted to bcd and the
|		digits are stored in the final string.
|		Test the length of the final exponent string.  If the
|		length is 4, set operr.
|
|	A16.	Write sign bits to final string.
|
|	Implementation Notes:
|
|	The registers are used as follows:
|
|		d0: scratch; LEN input to binstr
|		d1: scratch
|		d2: upper 32-bits of mantissa for binstr
|		d3: scratch;lower 32-bits of mantissa for binstr
|		d4: LEN
|		d5: LAMBDA/ICTR
|		d6: ILOG
|		d7: k-factor
|		a0: ptr for original operand/final result
|		a1: scratch pointer
|		a2: pointer to FP_X; abs(original value) in ext
|		fp0: scratch
|		fp1: scratch
|		fp2: scratch
|		F_SCR1:
|		F_SCR2:
|		L_SCR1:
|		L_SCR2:

|		Copyright (C) Motorola, Inc. 1990
|			All Rights Reserved
|
|       For details on the license for this file, please see the
|       file, README, in this same directory.

|BINDEC    idnt    2,1 | Motorola 040