1 | /*
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2 | =============================================================================
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3 | dec2fr.c -- Buchla 700 fractional 2's complement conversion functions
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4 | Version 10 -- 1987-12-06 -- D.N. Lynx Crowe
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5 | =============================================================================
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6 | */
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7 |
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8 | #define TESTER 0
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9 |
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10 | #include "stddefs.h"
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11 | #include "stdio.h"
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12 |
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13 | #define SFACT 1000L /* scale factor */
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14 |
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15 | static int32_t d2f[][10] = { /* decimal to fraction table */
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16 |
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17 | {0x00000000L, 0x000019A0L, 0x00003336L, 0x00004CD0L, 0x00006668L,
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18 | 0x00008000L, 0x000099A0L, 0x0000B336L, 0x0000CCCEL, 0x0000E668L},
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19 |
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20 | {0x00000000L, 0x00000290L, 0x00000520L, 0x000007B0L, 0x00000A40L,
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21 | 0x00000CD0L, 0x00000F60L, 0x000011F0L, 0x00001480L, 0x00001710L}
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22 | };
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23 |
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24 | static int32_t f2d[] = { /* fraction to decimal table */
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25 |
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26 | 50000L, 25000L, 12500L, 6250L,
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27 | 3125L, 1562L, 781L, 390L,
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28 | 195L, 97L, 48L, 24L,
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29 | 12L, 6L, 3L, 1L
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30 | };
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31 |
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32 | /* |
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33 |
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34 | */
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35 |
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36 | /*
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37 | =============================================================================
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38 | dec2fr() -- convert an ASCII decimal string to fractional binary
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39 |
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40 | The input string is 4 characters in the range 100- to 100+ inclusive.
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41 | The result is a 2's complement binary fractional value.
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42 | =============================================================================
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43 | */
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44 |
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45 | int16_t dec2fr(int8_t *s)
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46 | {
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47 | register int16_t i;
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48 |
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49 | if (s[0] EQ '1') {
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50 |
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51 | if (s[1] EQ '0') {
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52 |
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53 | if (s[2] EQ '0') {
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54 |
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55 | if (s[3] EQ '-')
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56 | return(0x8000); /* -100 */
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57 | else
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58 | return(0x7FFF); /* +100 */
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59 |
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60 | } else {
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61 |
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62 | return(0xFFFF); /* ERROR */
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63 | }
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64 |
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65 | } else {
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66 |
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67 | return(0xFFFF); /* ERROR */
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68 |
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69 | }
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70 |
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71 | /* |
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72 |
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73 | */
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74 |
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75 | } else if (s[0] EQ '0') {
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76 |
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77 | i = (d2f[0][s[1] - '0'] + d2f[1][s[2] - '0']) >> 1;
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78 |
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79 | if (s[3] EQ '-') {
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80 |
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81 | if (i)
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82 | return(~i); /* negative number */
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83 | else
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84 | return(0); /* zero is always 0 */
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85 |
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86 | } else {
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87 |
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88 | return(i); /* positive number */
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89 | }
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90 | }
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91 |
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92 | return(0xFFFF); /* ERROR */
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93 | }
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94 |
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95 | /* |
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96 |
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97 | */
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98 |
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99 | /*
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100 | =============================================================================
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101 | fr2dec() -- convert a 2's complement fraction to decimal ASCII notation
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102 |
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103 | The input is a 2's complement binary fractional value.
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104 | The result string is 4 characters in the range 100- to 100+ inclusive.
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105 | =============================================================================
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106 | */
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107 |
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108 | int8_t *fr2dec(int16_t v, int8_t *s)
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109 | {
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110 | register int32_t acc, sc;
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111 | register int16_t i, p;
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112 |
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113 | if (v EQ 0x7FFF) { /* +100 */
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114 |
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115 | sprintf(s, "100+");
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116 | return(s);
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117 | }
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118 |
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119 | if (v EQ 0x8000) { /* -100 */
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120 |
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121 | sprintf(s, "100-");
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122 | return(s);
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123 | }
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124 |
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125 | if (v & 0x8000) {
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126 |
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127 | v = ~v; /* negative number */
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128 | p = '-';
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129 |
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130 | } else {
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131 |
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132 | p = '+'; /* positive number */
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133 | }
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134 |
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135 | acc = 0;
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136 |
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137 | for (i = 0; i LT 15; i++)
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138 | if (v & (1 << (14 - i)))
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139 | acc += f2d[i];
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140 |
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141 | sc = SFACT;
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142 | acc /= sc;
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143 | sprintf(s, "%03d%c", (int16_t)acc, p);
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144 | return(s);
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145 | }
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146 |
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147 | /* |
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148 |
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149 | */
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150 |
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151 | #if TESTER
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152 |
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153 | #include "stdio.h"
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154 |
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155 | #include "stdio.h"
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156 |
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157 | extern int memcmp();
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158 |
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159 | char t[8], v[8];
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160 |
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161 | /*
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162 | =============================================================================
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163 | test program for fractional two's complement conversion functions
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164 | =============================================================================
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165 | */
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166 |
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167 | main()
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168 | {
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169 | register short i;
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170 | register short u;
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171 |
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172 | for (i = 0; i < 101; i++) {
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173 |
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174 | if (i EQ 50)
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175 | printf("\f");
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176 |
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177 | sprintf(t, "%03d+", i);
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178 | u = dec2fr(t);
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179 |
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180 | if (u EQ 0xFFFF) {
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181 |
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182 | printf("[%s] = ERROR = ?????? ", t);
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183 |
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184 | } else {
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185 |
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186 | fr2dec(u, v);
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187 | printf("[%s] = 0x%04x = [%s]", t, u, v);
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188 | }
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189 |
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190 | printf(" %s ", memcmp(t, v, 4) ? "<--" : " ");
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191 |
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192 | sprintf(t, "%03d-", i);
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193 | u = dec2fr(t);
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194 |
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195 | if (u EQ 0xFFFF) {
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196 |
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197 | printf(" [%s] = ERROR = ??????\n", t);
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198 |
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199 | } else {
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200 |
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201 | fr2dec(u, v);
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202 | printf(" [%s] = 0x%04x = [%s]", t, u, v);
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203 | }
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204 |
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205 | printf(" %s\n", memcmp(t, v, 4) ? "<--" : "");
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206 |
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207 | }
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208 | }
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209 |
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210 | #endif
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