binstr.S (4302B)
1| 2| binstr.sa 3.3 12/19/90 3| 4| 5| Description: Converts a 64-bit binary integer to bcd. 6| 7| Input: 64-bit binary integer in d2:d3, desired length (LEN) in 8| d0, and a pointer to start in memory for bcd characters 9| in d0. (This pointer must point to byte 4 of the first 10| lword of the packed decimal memory string.) 11| 12| Output: LEN bcd digits representing the 64-bit integer. 13| 14| Algorithm: 15| The 64-bit binary is assumed to have a decimal point before 16| bit 63. The fraction is multiplied by 10 using a mul by 2 17| shift and a mul by 8 shift. The bits shifted out of the 18| msb form a decimal digit. This process is iterated until 19| LEN digits are formed. 20| 21| A1. Init d7 to 1. D7 is the byte digit counter, and if 1, the 22| digit formed will be assumed the least significant. This is 23| to force the first byte formed to have a 0 in the upper 4 bits. 24| 25| A2. Beginning of the loop: 26| Copy the fraction in d2:d3 to d4:d5. 27| 28| A3. Multiply the fraction in d2:d3 by 8 using bit-field 29| extracts and shifts. The three msbs from d2 will go into 30| d1. 31| 32| A4. Multiply the fraction in d4:d5 by 2 using shifts. The msb 33| will be collected by the carry. 34| 35| A5. Add using the carry the 64-bit quantities in d2:d3 and d4:d5 36| into d2:d3. D1 will contain the bcd digit formed. 37| 38| A6. Test d7. If zero, the digit formed is the ms digit. If non- 39| zero, it is the ls digit. Put the digit in its place in the 40| upper word of d0. If it is the ls digit, write the word 41| from d0 to memory. 42| 43| A7. Decrement d6 (LEN counter) and repeat the loop until zero. 44| 45| Implementation Notes: 46| 47| The registers are used as follows: 48| 49| d0: LEN counter 50| d1: temp used to form the digit 51| d2: upper 32-bits of fraction for mul by 8 52| d3: lower 32-bits of fraction for mul by 8 53| d4: upper 32-bits of fraction for mul by 2 54| d5: lower 32-bits of fraction for mul by 2 55| d6: temp for bit-field extracts 56| d7: byte digit formation word;digit count {0,1} 57| a0: pointer into memory for packed bcd string formation 58| 59 60| Copyright (C) Motorola, Inc. 1990 61| All Rights Reserved 62| 63| For details on the license for this file, please see the 64| file, README, in this same directory. 65 66|BINSTR idnt 2,1 | Motorola 040 Floating Point Software Package 67 68 |section 8 69 70#include "fpsp.h" 71 72 .global binstr 73binstr: 74 moveml %d0-%d7,-(%a7) 75| 76| A1: Init d7 77| 78 moveql #1,%d7 |init d7 for second digit 79 subql #1,%d0 |for dbf d0 would have LEN+1 passes 80| 81| A2. Copy d2:d3 to d4:d5. Start loop. 82| 83loop: 84 movel %d2,%d4 |copy the fraction before muls 85 movel %d3,%d5 |to d4:d5 86| 87| A3. Multiply d2:d3 by 8; extract msbs into d1. 88| 89 bfextu %d2{#0:#3},%d1 |copy 3 msbs of d2 into d1 90 asll #3,%d2 |shift d2 left by 3 places 91 bfextu %d3{#0:#3},%d6 |copy 3 msbs of d3 into d6 92 asll #3,%d3 |shift d3 left by 3 places 93 orl %d6,%d2 |or in msbs from d3 into d2 94| 95| A4. Multiply d4:d5 by 2; add carry out to d1. 96| 97 asll #1,%d5 |mul d5 by 2 98 roxll #1,%d4 |mul d4 by 2 99 swap %d6 |put 0 in d6 lower word 100 addxw %d6,%d1 |add in extend from mul by 2 101| 102| A5. Add mul by 8 to mul by 2. D1 contains the digit formed. 103| 104 addl %d5,%d3 |add lower 32 bits 105 nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90) 106 addxl %d4,%d2 |add with extend upper 32 bits 107 nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90) 108 addxw %d6,%d1 |add in extend from add to d1 109 swap %d6 |with d6 = 0; put 0 in upper word 110| 111| A6. Test d7 and branch. 112| 113 tstw %d7 |if zero, store digit & to loop 114 beqs first_d |if non-zero, form byte & write 115sec_d: 116 swap %d7 |bring first digit to word d7b 117 aslw #4,%d7 |first digit in upper 4 bits d7b 118 addw %d1,%d7 |add in ls digit to d7b 119 moveb %d7,(%a0)+ |store d7b byte in memory 120 swap %d7 |put LEN counter in word d7a 121 clrw %d7 |set d7a to signal no digits done 122 dbf %d0,loop |do loop some more! 123 bras end_bstr |finished, so exit 124first_d: 125 swap %d7 |put digit word in d7b 126 movew %d1,%d7 |put new digit in d7b 127 swap %d7 |put LEN counter in word d7a 128 addqw #1,%d7 |set d7a to signal first digit done 129 dbf %d0,loop |do loop some more! 130 swap %d7 |put last digit in string 131 lslw #4,%d7 |move it to upper 4 bits 132 moveb %d7,(%a0)+ |store it in memory string 133| 134| Clean up and return with result in fp0. 135| 136end_bstr: 137 moveml (%a7)+,%d0-%d7 138 rts 139 |end