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
73 binstr:
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 |
83 loop:
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
115 sec_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
124 first_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 |
136 end_bstr:
137 moveml (%a7)+,%d0-%d7
138 rts
139 |end