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jcastillo |
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| binstr.sa 3.3 12/19/90
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| Description: Converts a 64-bit binary integer to bcd.
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| Input: 64-bit binary integer in d2:d3, desired length (LEN) in
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| d0, and a pointer to start in memory for bcd characters
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| in d0. (This pointer must point to byte 4 of the first
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| lword of the packed decimal memory string.)
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| Output: LEN bcd digits representing the 64-bit integer.
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| Algorithm:
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| The 64-bit binary is assumed to have a decimal point before
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| bit 63. The fraction is multiplied by 10 using a mul by 2
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| shift and a mul by 8 shift. The bits shifted out of the
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| msb form a decimal digit. This process is iterated until
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| LEN digits are formed.
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| A1. Init d7 to 1. D7 is the byte digit counter, and if 1, the
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| digit formed will be assumed the least significant. This is
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| to force the first byte formed to have a 0 in the upper 4 bits.
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| A2. Beginning of the loop:
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| Copy the fraction in d2:d3 to d4:d5.
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| A3. Multiply the fraction in d2:d3 by 8 using bit-field
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| extracts and shifts. The three msbs from d2 will go into
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| d1.
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| A4. Multiply the fraction in d4:d5 by 2 using shifts. The msb
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| will be collected by the carry.
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| A5. Add using the carry the 64-bit quantities in d2:d3 and d4:d5
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| into d2:d3. D1 will contain the bcd digit formed.
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| A6. Test d7. If zero, the digit formed is the ms digit. If non-
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| zero, it is the ls digit. Put the digit in its place in the
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| upper word of d0. If it is the ls digit, write the word
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| from d0 to memory.
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| A7. Decrement d6 (LEN counter) and repeat the loop until zero.
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| Implementation Notes:
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| The registers are used as follows:
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| d0: LEN counter
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| d1: temp used to form the digit
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| d2: upper 32-bits of fraction for mul by 8
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| d3: lower 32-bits of fraction for mul by 8
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| d4: upper 32-bits of fraction for mul by 2
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| d5: lower 32-bits of fraction for mul by 2
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| d6: temp for bit-field extracts
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| d7: byte digit formation word;digit count {0,1}
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| a0: pointer into memory for packed bcd string formation
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| Copyright (C) Motorola, Inc. 1990
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| All Rights Reserved
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| THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
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| The copyright notice above does not evidence any
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| actual or intended publication of such source code.
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|BINSTR idnt 2,1 | Motorola 040 Floating Point Software Package
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|section 8
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.include "fpsp.h"
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.global binstr
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binstr:
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moveml %d0-%d7,-(%a7)
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| A1: Init d7
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moveql #1,%d7 |init d7 for second digit
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subql #1,%d0 |for dbf d0 would have LEN+1 passes
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| A2. Copy d2:d3 to d4:d5. Start loop.
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loop:
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movel %d2,%d4 |copy the fraction before muls
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movel %d3,%d5 |to d4:d5
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| A3. Multiply d2:d3 by 8; extract msbs into d1.
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bfextu %d2{#0:#3},%d1 |copy 3 msbs of d2 into d1
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asll #3,%d2 |shift d2 left by 3 places
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bfextu %d3{#0:#3},%d6 |copy 3 msbs of d3 into d6
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asll #3,%d3 |shift d3 left by 3 places
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orl %d6,%d2 |or in msbs from d3 into d2
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| A4. Multiply d4:d5 by 2; add carry out to d1.
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asll #1,%d5 |mul d5 by 2
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roxll #1,%d4 |mul d4 by 2
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swap %d6 |put 0 in d6 lower word
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addxw %d6,%d1 |add in extend from mul by 2
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| A5. Add mul by 8 to mul by 2. D1 contains the digit formed.
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addl %d5,%d3 |add lower 32 bits
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nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90)
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addxl %d4,%d2 |add with extend upper 32 bits
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nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90)
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addxw %d6,%d1 |add in extend from add to d1
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swap %d6 |with d6 = 0; put 0 in upper word
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| A6. Test d7 and branch.
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tstw %d7 |if zero, store digit & to loop
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beqs first_d |if non-zero, form byte & write
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sec_d:
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swap %d7 |bring first digit to word d7b
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aslw #4,%d7 |first digit in upper 4 bits d7b
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addw %d1,%d7 |add in ls digit to d7b
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moveb %d7,(%a0)+ |store d7b byte in memory
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swap %d7 |put LEN counter in word d7a
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clrw %d7 |set d7a to signal no digits done
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dbf %d0,loop |do loop some more!
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bras end_bstr |finished, so exit
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first_d:
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swap %d7 |put digit word in d7b
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movew %d1,%d7 |put new digit in d7b
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swap %d7 |put LEN counter in word d7a
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addqw #1,%d7 |set d7a to signal first digit done
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dbf %d0,loop |do loop some more!
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swap %d7 |put last digit in string
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lslw #4,%d7 |move it to upper 4 bits
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moveb %d7,(%a0)+ |store it in memory string
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| Clean up and return with result in fp0.
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end_bstr:
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moveml (%a7)+,%d0-%d7
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rts
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|end
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