projects / pdp8.git / blame
| Commit | Line | Data |
|---|---|---|
| 84b5715c PH |
1 | SECT WORDS\r |
| 2 | /FILE GETWRD\r | |
| 3 | /Version 02.06\r | |
| 4 | \r | |
| 5 | /This module contains two entry points to allow FORTRAN\r | |
| 6 | /programs access to the contents of any of the 3 12-bit words\r | |
| 7 | /in any floating point variable. The idea is to facilitate\r | |
| 8 | /operations on text strings which are stored as 8-bit ASCII,\r | |
| 9 | /such as input by the routine RDLIN (see write up for RDLIN\r | |
| 10 | /included with that routine.).\r | |
| 11 | \r | |
| 12 | / ROUTINE GETWRD\r | |
| 13 | \r | |
| 14 | /This routine is a function subroutine (ie: the result is\r | |
| 15 | /returned in the FAC). As such it's name may be used in arithmetic\r | |
| 16 | /statments and the returned data will be used directly. The\r | |
| 17 | /following example illustrates it's use:\r | |
| 18 | / .\r | |
| 19 | / .\r | |
| 20 | / RESULT=GETWRD(MESSAG,INDX,MASK)\r | |
| 21 | / .\r | |
| 22 | / .\r | |
| 23 | \r | |
| 24 | /Here, the desired word (exponent,hi or lo mantissa) will\r | |
| 25 | /be returned and placed into the variable RESULT. The argument\r | |
| 26 | /MESSAG may be a variable or an array. The actual address in the\r | |
| 27 | /array will be computed by the routine, depending on the value\r | |
| 28 | /of the variable INDX. INDX points to the specific 12-bit word in\r | |
| 29 | /the array you want. The routine adds this number to the start\r | |
| 30 | /address of the array, and operates on this word with an XTA\r | |
| 31 | /instruction.\r | |
| 32 | \r | |
| 33 | /The following table illustrates this conversion:\r | |
| 34 | \r | |
| 35 | /Value of INDX Element word Array element\r | |
| 36 | \r | |
| 37 | / 1 Exponent 1\r | |
| 38 | / 2 Hi mant. 1\r | |
| 39 | / 3 Lo mant. 1\r | |
| 40 | / 4 Exponent 2\r | |
| 41 | / 5 Hi mant. 2\r | |
| 42 | / etc. etc. etc.\r | |
| 43 | \r | |
| 44 | /The argument MASK allows the masking of the data retrieved\r | |
| 45 | /so parity bits etc. can be removed easily. The value should be\r | |
| 46 | /the decimal equivalent of the octal number you want the data masked\r | |
| 47 | /by. If MASK is 0, no masking takes place.\r | |
| 48 | \r | |
| 49 | / ROUTINE PUTWRD\r | |
| 50 | \r | |
| 51 | /This routine provides the converse function of GETWRD.\r | |
| 52 | /It is called from FORTRAN using a standard subroutine call:\r | |
| 53 | \r | |
| 54 | / CALL PUTWRD(MESSAG,INDX,WORD)\r | |
| 55 | \r | |
| 56 | /The first 2 arguments are identical to those in the routine GETWRD,\r | |
| 57 | /but the third argument reflects the difference in function of\r | |
| 58 | /these two routines. WORD is the value in decimal that is to\r | |
| 59 | /be placed into the 12-bit word referenced by the first two\r | |
| 60 | /arguments. Masking is not provided for.\r | |
| 61 | \r | |
| 62 | EXTERN #RETRN\r | |
| 63 | EXTERN #ARGER\r | |
| 64 | ENTRY GETWRD\r | |
| 65 | ENTRY PUTWRD\r | |
| 66 | \r | |
| 67 | \r | |
| 68 | /Little routine to do masking of octal data.\r | |
| 69 | /Although the references to XR 0 and 1 destroy the\r | |
| 70 | /value of the Array element in XR 0-2, this is of no\r | |
| 71 | /consequence because we've already finished using it.\r | |
| 72 | \r | |
| 73 | /The only caveat here is that #XR+2 is not an auto index register\r | |
| 74 | /Calling in #PAGE0 won't help because we could ge loaded onto\r | |
| 75 | /page 0 of some other field.\r | |
| 76 | \r | |
| 77 | SECT8 #MASK\r | |
| 78 | TAD #XR /Index 0 contains fetched data\r | |
| 79 | AND #XR+1 /Index 1 contains the mask.\r | |
| 80 | DCA #XR /Apply mask to data\r | |
| 81 | CIF CDF /Reset data field\r | |
| 82 | JMP% #XR+2 /XR5 contains return address\r | |
| 83 | \r | |
| 84 | /FPP code starts here. It is intended that it be contiguous\r | |
| 85 | /with the 8-mode code so the rest of the page is not wasted\r | |
| 86 | \r | |
| 87 | SECNAM, TEXT +GETWRD+ /Init for traceback\r | |
| 88 | #BASE, ORG .+3 /Base 0\r | |
| 89 | INDX, ORG .+3 /Base 1: Stuff addresses in here\r | |
| 90 | #PTWRD, TEXT +PUTWRD+ /Base 2: One of the section names\r | |
| 91 | #GTWRD, TEXT +GETWRD+ /Base 3: The other section name\r | |
| 92 | \r | |
| 93 | /Relative address on page is 23. This puts XR+2 out of any possible\r | |
| 94 | /danger with respect to auto-index registers.\r | |
| 95 | \r | |
| 96 | #XR, FNOP /Base 4: XR0-2\r | |
| 97 | ADDR #RETRN / #XR2=return to FRTS address\r | |
| 98 | 1;2;3 /Base 5: XR3-5\r | |
| 99 | /TENK, F 4096.0 /Base 6\r | |
| 100 | K2048, F 2048.0\r | |
| 101 | XSETX, 27;47;7777 /Base 7: SETX-JA-1\r | |
| 102 | \r | |
| 103 | ORG #BASE+30\r | |
| 104 | FNOP; JA #BASE /Pointer to section name+3\r | |
| 105 | FNOP;#GOBAK, 0;0 /Pointer to calling base page\r | |
| 106 | \r | |
| 107 | /Routine starts here. Details of index register usage are\r | |
| 108 | /as follows:\r | |
| 109 | \r | |
| 110 | / XR 0 Used to fetch/store/hold target word\r | |
| 111 | / XR 1 Used as arg. fetch index, and to hold mask word\r | |
| 112 | / XR 2 Contains the FRTS TRAP return address\r | |
| 113 | / XR 3 =1 to fetch ARRAY arg\r | |
| 114 | / XR 4 =2 to fetch INDEX arg\r | |
| 115 | / XR 5 =3 to fetch WORD/MASK arg\r | |
| 116 | \r | |
| 117 | BASE #BASE /Tell assembler wher the base page is\r | |
| 118 | \r | |
| 119 | /Enter here for PUTWRD\r | |
| 120 | \r | |
| 121 | PUTWRD, FLDA #PTWRD,0 /Get putwrd name\r | |
| 122 | JSA GETARG /Get args set up\r | |
| 123 | \r | |
| 124 | FLDA% INDX /Load the new value for target word\r | |
| 125 | JLT TSTNEG /Negative range check\r | |
| 126 | FSUB K2048 /For positive, < 2048\r | |
| 127 | JGE PUTERR /Out of range\r | |
| 128 | JA OK /Else ok\r | |
| 129 | TSTNEG, FADD K2048 /Neg more than 2048?\r | |
| 130 | JLE PUTERR /Yes, errror\r | |
| 131 | OK, FLDA% INDX\r | |
| 132 | FLDA% INDX /In range\r ATX 0 /Store it\r | |
| 133 | JA #GOBAK /Return\r | |
| 134 | \r | |
| 135 | PUTERR, FLDA SECNAM\r | |
| 136 | TRAP4 #ARGER\r | |
| 137 | \r | |
| 138 | /Enter here for GETWRD\r | |
| 139 | \r | |
| 140 | GETWRD, FLDA #GTWRD,0 /Load section name\r | |
| 141 | JSA GETARG /Get things set up\r | |
| 142 | \r | |
| 143 | XTA 0 /Get the target word\r | |
| 144 | SETX #XR /Reset index registers\r | |
| 145 | ATX 0 /Store word in XR 0\r | |
| 146 | \r | |
| 147 | FLDA% INDX /Get the mask value\r | |
| 148 | JEQ NOMASK /If 0, skip masking\r | |
| 149 | ATX 1 /Put the mask value into an index\r | |
| 150 | TRAP3 #MASK /Go mask the number\r | |
| 151 | \r | |
| 152 | NOMASK, XTA 0 /Recover the masked number\r | |
| 153 | / JGE #GOBAK /If result is positive, return now\r | |
| 154 | / FADD TENK /Otherwise, un-2's complement first\r | |
| 155 | JA #GOBAK /Return the answer in FAC\r | |
| 156 | \r | |
| 157 | /Both routines come here to get things set up. FAC contains\r | |
| 158 | /section name.\r | |
| 159 | \r | |
| 160 | \r | |
| 161 | GETARG, 0;0\r | |
| 162 | FSTA SECNAM /Name into traceback prologue\r | |
| 163 | SETX #XR /Set address of index registers\r | |
| 164 | \r | |
| 165 | STARTD /Mode for addresses\r | |
| 166 | 0210 /Load pointer to callers prologue\r | |
| 167 | FSTA #GOBAK,0 /Store as return address\r | |
| 168 | 0200 /Load address of argument list\r | |
| 169 | SETB #BASE /Now tell FPP where the base page is\r | |
| 170 | \r | |
| 171 | FSTA #BASE /Store address of args\r | |
| 172 | \r | |
| 173 | FLDA% #BASE,4 /Load pointer to INDX\r | |
| 174 | FSTA INDX /Store this\r | |
| 175 | \r | |
| 176 | STARTF /Mode for numbers\r | |
| 177 | FLDA% INDX /Load the pointer\r | |
| 178 | ALN 0 /Fix it\r | |
| 179 | STARTD /Address mode\r | |
| 180 | \r | |
| 181 | FADD% #BASE,3 /Add address of ARRAY/VARIABLE\r | |
| 182 | FADD XSETX /Create a SETX ARRAY+INDEX-1\r | |
| 183 | FSTA ZSETX,0 /Store to execute in line\r | |
| 184 | \r | |
| 185 | FLDA% #BASE,5 /Load pointer to MASK/Replacement word\r | |
| 186 | FSTA INDX /Store this\r | |
| 187 | STARTF /Set numeric mode\r | |
| 188 | \r | |
| 189 | ZSETX, SETX . /Set index on target word\r | |
| 190 | JA GETARG /Return, everything set\r |